SYSTEM AND METHOD FOR IMPROVED ROAD INFORMATION

FIELD

The present invention relates to a system and method for improving map data representing a road network for navigational devices, and in particular, but not being limited to, providing map data for routing algorithms in a navigational device to identify optimal or alternative paths for negotiating around particular points of a road network.

BACKGROUND

In this specification where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned.

Various navigational devices are available for plotting a vehicle travel path to a destination via links (roads). Conventional navigation systems can detect a present position by using a global positioning system (GPS) and map matching functions in the navigational devices. Typically, the current position is presented on a road map depicted on a display screen, and the operator is guided along a suitable route set from a first point (such as the present position) to a second point being a desired destination. The route may be set based upon the Dijkstra algorithm or a similar method based on stored road map data. The route may be determined from the present position to nodes (usually intersections) by using map data stored in a static data source such as a CD-ROM, DVD or any other form of media used for data storage and by using link data for the links among the nodes. Links, having a minimum cost, are connected together to set a route to the destination after all costs up to the destination have been calculated.

Navigational devices can give the operator a choice of operation modes for setting a route. These modes may include a time-priority mode for setting a route that minimizes the travelling time, a distance-priority mode for setting a route that minimizes the travelling distance, and a common road-priority mode for setting a route that avoids toll roads as much as possible.

For the time-priority mode, the time needed for passing along a given road is calculated based on expected average vehicle speeds, and a combination of roads is selected such that the sum of travel times from the start point to the destination is a minimum. Similarly, for the distance- priority mode, a combination of roads are selected such that the distance travelled from a start point to a destination is a minimum. However, a navigation device needs to analyse the combined time or distance parameters of a large number of combinations of different roads in

order to recommend an optimal path in terms of travel distance or travel time. This increases the delay for providing suitable directions to a user of such a navigational device. The delay may be decreased if the navigational device analyses fewer road combinations, but the optimal path determined by the device may not be the best option since some road combinations were not taken account when determining that recommendation.

The map data used by a navigational device for calculating a route may incorporate a state or national road hierarchy classification system. A road hierarchy defines each of the roads in a road network in terms of its function or importance, so that correct design criteria, upgrading, maintenance and road system management are applied. For example, large or high volume roads (such as expressways and freeways) with grade separated intersections are given an 'M' class in the hierarchy. High volume roads that are not necessarily grade separated at intersections are an 'A' class in the hierarchy. Smaller, medium volume prefectural roads, city or town roads are 'B' class in the hierarchy. Small, low volume sealed or semi-sealed roads are 'C class in the hierarchy.

Road hierarchy classification and criteria may vary between different jurisdictions. For example, in Australia, there is no official federal road hierarchy. Each state has its own hierarchy systems that terminate at state borders and there is no connectivity or consistency between jurisdictions. In some jurisdictions many roads remain unclassified because they do not meet minimum requirements for classification, such as roads that do not have sufficient traffic, are too short, that have been privately constructed, or are located in a remote area outside the zone for which the road hierarchy is defined. Furthermore, some of the classified roads are of restricted traffic-type, for example, roads that are too narrow for certain types of vehicles, road that can take only one-way traffic, road that allow only left or right hand turns at particular streets/intersections, and so forth.

Conventional navigation systems do not use restricted-type roads in the recommended travel path determination process, because data relating to the restricted-type roads are in many cases incomplete or unreliable. A route between two points is calculated based predominantly on the M, A, B and C class roads data available, excluding restricted-type roads from the calculation, with priority given to the roads with the highest classification. Accordingly, a recommended travel path may include unnecessary detours, even though other roads, including some restricted-type roads are in fact available for vehicle travel.

Routing algorithms may recommend an optimal path for travelling from a point of origin to a destination. However, such algorithms rarely take into account physical restrictions (such as

road barriers and manoeuvring constraints) at specific points (such as road junctions) in a road network. Furthermore, navigational devices using such algorithms typically rely on static data which do not reflect unpredictable changes in traffic condition. Thus, such devices are unable to issue reliable instructions to users in a timely manner in response to changes in traffic condition or manoeuvring constraints (e.g. direct drivers along an alternative route in response to a traffic accident or as a result of changes in turn restrictions shown by signs).

It is therefore desired to address one or more of the above, or to at least provide a useful alternative.

SUMMARY

According to the present invention there is provided a system for improving map data for navigational devices, said system being configured for:

i) accessing map data representing a closed hierarchical network of roads based on a closed network of functional road class values allocated to said roads within a predetermined geographical region;

ii) accessing rules data representing attributes of nodes associated with one or more of said roads, said attributes including manoeuvring restrictions at the location of said nodes;

iii) adjusting, based on said rules data, said functional road class values for an alternate route including one or more of said roads adjacent to a selected one of said nodes being associated with a traffic restriction, said alternate route for traffic to negotiate past said selected node to reach a destination in a nominated direction of travel; and

iv) updating said map data to include said adjusted functional road class values, such that a said navigation system, when using the updated said map data, is able to direct traffic via said alternate route.

The present invention also provides a system for enhancing road system data for navigational devices, said system being configured for:

i) accessing road system data representing a transportation network having a plurality of interconnected paths and nodes joining said paths, said road system data including path data representing attributes of said paths, said attributes including functional classes for respective said paths, and rules data representing manoeuvring constraints at said nodes;

ii) selecting, based on said path data and rules data, a route with one or more interconnected said paths adjacent to a selected said node, said route for traffic to negotiate past said selected node to reach a destination in a nominated direction of travel;

iii) adjusting said functional classes for the paths included in said route to represent greater preference for traffic to use of said route when compared with the functional classes for other said paths adjacent to said selected node; and

iv) generating enhanced said road system data including said adjusted functional classes, to enable a said navigational device, when using said road system data, to direct traffic via said route.

The present invention also provides a method for improving map data for navigational devices, including:

i) accessing map data representing a closed hierarchical network of roads based on a closed network of functional road class values allocated for each of said roads within a predetermined geographical region;

ii) accessing rules data representing attributes of nodes associated with one or more of said roads, said attributes including manoeuvring restrictions at the location of said nodes;

iii) adjusting, based on said rules data, said functional road class values for an alternate route including one or more of said roads adjacent to a selected one of said nodes being associated with a traffic restriction, said alternate route for traffic to negotiate past said selected node to reach a destination in a nominated direction of travel; and

iv) updating said map data to including said adjusted functional road class values, such that a said navigation system, when using the updated said map data, is able to direct traffic via said alternate route.

The present invention also provides a method for enhancing road system data for navigational devices, including:

i) accessing road system data representing a transportation network having a plurality of interconnected paths and nodes joining said paths, said road system data including path data representing attributes of said paths, said attributes including functional classes for respective said paths, and rules data representing manoeuvring constraints at said nodes;

ii) selecting, based on said path data and rules data, a route with one or more interconnected said paths adjacent to a selected said node, said route for traffic to negotiate past said selected node to reach a destination in a nominated direction of travel;

iii) adjusting said functional classes for the paths included in said route to represent greater preference for traffic to use of said route when compared with the functional classes for other said paths adjacent to said selected node; and

iv) generating enhanced said road system data including said adjusted functional classes, to enable a said navigational device, when using said road system data, to direct traffic via said route.

The present invention also provides a data structure for navigations devices, including:

i) map data representing a closed hierarchical network of roads based on a closed network of functional road class values allocated for each of said roads within a predetermined geographical region;

ii) rules data representing attributes of nodes for one or more of said roads, said attributes including manoeuvring restrictions at the location of said nodes;

wherein said map data includes adjusted said functional road class values for at least a portion of said roads in the vicinity of a restriction associated with a selected one of the nodes, said adjustment being based on said attributes.

The present invention also provides a navigational device using or incorporating a data structure as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention are herein described, by way of example only, with reference to the accompanying drawings, wherein:

Figure 1 is a block diagram showing the components of the map enhancement system;

Figure 2 is a flow diagram of steps performed under the control of the system;

Figure 3 is a diagram representing actual road restrictions in a suburban area;

Figure 4 is a diagram representing sign prohibited turn restrictions on roads in an area;

Figure 5 is a diagram representing vehicle and time dependant restrictions on roads in an area;

Figure 6 is a diagram representing lane relational information for a road;

Figure 7 is a diagram representing land relational information for a road

Figure 8 is a map showing the road configuration in a first region;

Figure 9 is a map showing the road configuration in a second region.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The map enhancement system 100, as shown in Figure 1, includes a map editing module 102 and a database 104. The map editing module 102 accesses map data stored in the database 104 (e.g. map data corresponding to a selected geographical region). A user controls the map editing module 102 (e.g. via a user input interface or device) to change various data components of the map data received by module 102. For example, a user reviews the map data for various paths in the road network, and then selects (e.g. with the assistance of aerial imagery showing the physical size and volume of traffic on roads) one or more paths for negotiating past a particular node. Alternatively, the map editing module 102 analyses the map data to identify nodes that could potentially cause traffic congestion, and then analyses different combinations of paths adjacent a selected one of the identified nodes to identify an optimum path for negotiating past the selected node. The map editing module 102 modifies the accessed portion of map data based on the user's input and/or other predefined instructions. The map editing module 102 then instructs the database 104 to update the relevant portion of the map data to reflect the modifications made by the map editing module 102.

The map editing module 102 is provided by computer program code in languages such as C or C#, and the database 104 by a database server such as MySQL (http://www.mysql.org). all of which are executed on a standard personal computer (such as that provided by IBM Corporation <http://www.ibm.com>) running a standard operating system, such as Windows™ or Unix. Those skilled in the art will also appreciate that the processes performed by the map editing module 102 and database 104 can also be executed at least in part by dedicated hardware circuits, e.g. Application Specific Integrated Circuits (ASICs) or Field- Programmable Gate Arrays (FPGAs).

The map data stored in the database 104 is accessible by a navigational device 108 via a communications network 108 (such as the Internet or a wireless communications network such as WiFi, GPRS or 802.1 la/b/g network). Alternatively, the map data stored in the database 104 can be stored onto portable data storage media or any data storage device (such as an optical storage media) that is accessible by the navigational device.

The database 104 stores map data representing a transportation network having a plurality of interconnected paths (or lines) and nodes joining the paths. For example, the transportation network may correspond to a land-based road network. In a road network, paths may correspond to strips of land or physical structures on which traffic can travel (such as roads, streets, passovers, freeways and motorways). The map data may represent a road as being made up of one or more interconnected paths. Nodes (or points) correspond to junctions between different paths (such as a T-intersection).

The map data stored in the database 104 includes path data and rules data. The path data represents attributes of each path (e.g. roads) in the transportation network, including physical features or logical (e.g. classification) attributes associated with each of the paths. The attributes represented by the path data may include any of the characteristics of roads as defined in the International Standard Organisation (ISO) standard ISO 14825 (ISO/TC204/N629) relating to Geographic Data Files. The path data for a particular path may include one or more of the following:

1 functional class data representing a value (i.e. FRC value) indicating the functional type or importance of the path (e.g. the functional road class for the nominated portion of the road). The functional class values of paths may be classified as follows:

• A path with an FRC value of 0 represents a main road (e.g. a Motorways or M class roads);

• A path with an FRC value of 1 represents a first class road (e.g. major roads/national highway network or A class roads);

• A path with an FRC value of 2 represents a second class road (e.g. state road network or A or B class roads);

• A path with an FRC value of 3 represents a third class road (e.g. state interconnecting network or B class roads);

• A path with an FRC value of 4 represents a forth class road (e.g. major connecting roads or C class roads);

• A path with an FRC value of 5 represents a fifth class road (e.g. minor connecting roads suburb - suburb);

• A path with an FRC value of 6 represents a sixth class road (e.g. destination and destination collector roads);

• A path with an FRC value of 7 represents a seventh class road (e.g. destination dead-end roads);

• A path with an FRC value of 8 represents a eighth class road (e.g. walking tracks, pedestrian roads etc); and

• A path with an FRC value of 9 represents a ninth class road (for lower level paths);

2 speed attribute data representing the greatest permissible travel speed on the path;

3 distance data representing the travel length of the path;

4 physical attribute data representing the presence and type of barriers or physical restrictions adjacent to the path (e.g. physical barriers like concrete or concrete and paint median strips, walls, grassed and or vegetated divider, parking bays and shopping centres with significant level of pedestrian access that can potentially slow traffic);

5 time attribute data representing any travel restrictions applicable during predefined periods of the day (such as a lower speed limit in a school zone applicable during predefined periods of a day, or other restrictions that apply for different days of the week); and

6 access restriction data representing the types of vehicles allowed access to the path, such as restrictions based on vehicle weight or vehicle type (e.g. determined by number of axles, length of vehicle, maximum number of passengers on vehicle, and vehicle classification - such as car, truck, taxi, bus, bicycle, etc.).

The rules data represents manoeuvring constraints for different nodes (and optionally, for paths). The rules data for paths represents the general traffic rules for travelling on that path (such as the direction of travel and which side traffic should travel on). The rules data for a particular node may include:

i) manoeuvring constraints data representing whether particular types of turns are permissible at a particular node (as defined by traffic control signs or physical barriers relative to that node - such as prohibited access, all traffic must flow in a particular direction, and keep left or keep right restrictions);

ii) access constraints data whether some paths only allow travel in one direction (which affects the manoeuvring constraints at nodes); and/or

iii) traffic messaging channel incident (TMC) data representing a TMC value used to represent the existence of (and/or the type of) a traffic incident, restriction or congestion at a particular node. For example, different TMC values are used represent different types of traffic incidents, restrictions or congestion (e.g. including road works, traffic accidents, flooding, or changes in traffic flow conditions).

The map enhancement system 100 includes a processor (e.g. for executing instructions generated by the map editing module 102) that is configured for:

i) accessing map data representing a closed hierarchical network of roads based on a closed network of functional road class values allocated to the roads within a predetermined geographical region;

ii) accessing rules data representing attributes of nodes associated with one or more of the roads, the attributes including manoeuvring restrictions at the location of the nodes;

iii) adjusting, based on the rules data, the functional road class values for an alternate route including one or more of the roads adjacent to a selected one of the nodes being associated with a traffic restriction, the alternate route for traffic to negotiate past the selected node to reach a destination in a nominated direction of travel; and

iv) updating the map data to include the adjusted functional road class values, such that a the navigation system, when using the updated map data, is able to direct traffic via the alternate route.

This enables a navigational device to determine an optimal route between two locations based on the functional road class values for any of the roads in the region, and is able to determine the alternate route between the two locations based on the functional road class values for other the roads not in the optimal route. Also, the step of adjusting preferably includes:

selecting, based on the map data, the alternate route with one or more interconnected the roads adjacent to a selected one of the nodes, the route for traffic to negotiate past the selected node to reach a destination in a nominated direction of travel; and

adjusting the functional road class values for the roads included in the alternate route to represent greater preference for traffic to use of the route when compared with the functional road class values for other the roads adjacent to the selected node.

Preferably, the alternate route represents the one or more the roads that enables traffic to negotiate past the selected node in the least amount of time. Alternatively, the alternate route

represents the one or more roads that enables traffic to negotiate past the selected node by travelling the least distance.

The map enhancement system 100 could also be configured for:

assigning a group of one or more of the nodes to predetermined positions on a selected one of the roads in the region; and

allocating, to at least a selected one of the nodes in the group, a traffic messaging channel incident value representing a traffic incident at the location of the selected node that can be updated in real time; and

adjusting, based on the traffic messaging channel incident value for the selected node, the functional road class values for at least a portion of the roads in the vicinity of the selected node.

The map enhancement system 100 performs a map enhancement method under the control of the map editing module 102. The map enhancement system 100 performs a method of providing improved road system information suitable for use in vehicular navigation systems, the method including the step of allocating functional road class (FRC) values to each of the roads in an area based on attributes of road elements to create a closed hierarchical system FRC values, such that a vehicle navigation system can calculate the optimal route between two locations using the FRC value for any of the roads in the area.

The method performed by the map enhancement system 100 may further comprise the step of assigning one or more nodes to predetermined positions on the roads in the area and allocating to those one or more nodes a traffic messaging channel incident value (TMC value) that can be updated in real time, wherein updates to the TMC value is taken into account to adjustment to the FRC value for a portion of road in the vicinity of a node. For example, a TMC value represents a traffic interruption (e.g. an accident) at a particular node, which in effect, is represented by access or manoeuvring restrictions for that node.

The map enhancement system 100 may be configured to perform a method of providing improved road system data suitable for use in navigational devices, the method comprising:

(a) allocating a closed network FRC values to each of the roads within and to adjoining areas within a predetermined geographical region or location (e.g. on a national basis or within a defined suburban region),

(b) allocating attribution to nodes of one or more of the roads,

(c) adjusting the FRC value for at least a portion of the road in the vicinity of a restriction associated to the node in accordance with the attributes of road elements to create map data representing a closed hierarchical system of roads reflecting real world restrictions, such that a vehicle navigation system can calculate the optimal route between two locations using FRC values for any of the roads in the area as well recalculate an alternate route between two locations using FRC values for any of the alternate roads in the area.

The map enhancement system 100 may be further configured to provide a method of providing an improved road system suitable for use in navigational devices, the method comprising:

(a) allocating a closed network FRC values to each of the roads (or a group of one or more nodes at predetermined positions along such roads) within and to adjoining areas in a predetermined area (e.g. on a national basis),

(b) allocating TMC values to nodes (or points, lines and areas) of one or more of the roads. For example, TMC values may be allocated to secondary nodes of the transportation network, being nodes that represent a position (other than a junction of paths) along a particular path of the transportation network,

(c) adjusting the FRC value for at least a portion of the road (or to at least a selected one of the nodes in the group described above) in the vicinity of a node being associated with a restriction in accordance with the attributes of road elements to create a closed hierarchical road system reflecting real world restrictions, and

(d) allocating a TMC value to the nodes, wherein the TMC value can be updated in real time,

such that a navigational device can calculate the optimal route between two locations using FRC values and TMC values for any of the roads in the area as well re-calculate an alternate route between two locations using FRC values and TMC values for any of the alternate roads in the area..

The method may in addition allocate or adjust FRC values or TMC values for nodes or paths (e.g. points, paths or edges/lines of the roads).

In a preferred embodiment, a secondary node can also function as a primary node, such that the node is associated with both FRC and TMC values. In this embodiment a change to the TMC value will adjust the FRC value for at least a portion of the road in the vicinity of the node.

The functional road classes could be allocated, from an existing database of information such as for example, a national road network that includes motorways, major national roads, minor roads, collector roads and residential roads.

Typically, the FRC value for a road or a portion of road in the vicinity of a node is adjusted by 'upgrading' or 'downgrading' attributes of road elements in accordance with the real world restrictions and the need to create a hierarchal closed network of FRC values. Road elements include road attribute restrictions based on real world physical, implied and signposted confines. These road element restrictions are typically not included in any of the maps issued by federal, state or local government agencies. The road elements considered may include, for example:

• road geometry (e.g. narrow and winding),

• manoeuvre restrictions (e.g. no U-turn),

• accessibility of major and minor slip roads,

• exit and entry ramps,

• internal turning lanes,

• lane markings,

• physical barriers and median strips,

• temporary blockages (e.g. roadwork's),

• time dependant restrictions (e.g. emergency stopping lane becoming a transit lane at peak hour),

• tidal flow changes,

• traffic flow headings,

• sign posted mandatory movement restrictions,

• speed calming devices (e.g. road humps, speed or red light cameras),

• bypass roads,

• vehicle type restrictions (e.g. suitability for WD vehicles only), and

• significant landmark features.

Typically, the FRC value is initially adjusted due to permanent attributes of the road such as the presence of road humps, suitability for four wheel drive (4WD) vehicles only, grade separated crossings or the winding nature of the road.

The change in route planning as a result of an announced TMC incident is typically due to some dynamic, or transient attribute of the road such as road works in progress, occurrence of a traffic accident, stoppages due to public events, emergencies such as fire or flood. Thus the system of the present invention provides information to navigation devices that gives the driver alternate route options expected of a real world situation. Without a uniform and precise hierarchical system, users of a system that employ the data of the prior art experience routing guidance that does not reflect reality.

In a preferred embodiment, the map enhancement system 100 includes a suitable server and/or transmitter for transmitting TMC data stored in the database 104. The TMC data represents TMC values or instructions, and can be transmitted via a traffic messaging radio channel of the communications network 106 to navigation devices 108 capable of receiving radio wave transmissions. For example, the TMC data may include data indicating road blockage due to a traffic accident. The navigation device 108 can announce the presence of an incident and then re-calculate an alternative route taking into consideration alternate FRC values for different paths. TMC values assigned to the TMC database code (and thus FRC codes) may also updated at the same time to take into account changed traffic flow as people change routes to avoid the road blockage.

Typically, the TMC data would be supplied on a subscriber basis, such as by motoring clubs or any other data service provider to their members/users. The map data may be stored onto physical storage media (e.g. a DVD disc) that is supplied for use by the navigational device. TMC data may be transmitted to the navigational device via a separate radio channel (e.g. a Frequency-Modulated (FM) radio channel of a particular frequency used for a Radio Dispatch Service (RDS)). The navigation device can then identify the relevant nodes where there is a traffic incident or congestion based on the TMC data. The navigation device can then query the enhanced map data generated by the map enhancement system 100 to identify alternate routes for navigating past (e.g. going through or around) a selected one of the nodes in the transportation network (such as a node identified based on the TMC data).

The system 100 can be used to provide a standardised design of road networks such that users of navigational devices can experience consistent, relevant and accurate guidance advice. It

can enhance the driver's experience by removing routes that could be considered inappropriate or a prohibited by local government ordinance or restricted by physical design.

The map editing module 102 considers one or more of the following factors when considering changes to functional road classes (FRC) values to give appropriate guidance around a restriction (e.g. at a node).

When reviewing and adding database features that map real world traffic movement restrictions in the form of Sign Posted, physical barriers and grade separations, there is a requirement to investigate the need to amend the FRC values on other road geometry to provide a connected hierarchal network.

1 When adding a prohibited or mandatory turn restriction to the database, upgrades or downgrades to the FRC value of the relevant paths in the recommended alternate (or optimal) route must be made to ensure the above condition is maintained.

2 When adding a dual carriageway without a turning median break from adjoining roads to the database, upgrades or downgrades to the FRC values of the relevant paths in the recommended alternate (or optimal) route must be made to ensure the above condition is maintained.

3 When adding grade separation to multiple road elements in the database, upgrades or downgrades to the FRC values of the relevant paths in the recommended alternate (or optimal) route must be made to ensure the above condition is maintained.

In determining the need for an adjustment to the FRC value for a path, consideration must be given to, the availability of and the standard of, alternate roads in the local (or adjacent) area that are suitable for an upgrade.

Significance must be given to other impediments, restrictions and or obstructions (as defined by the path data or rules data), including:

• other sign posted restrictions on possible alternate routes;

• time dependant restrictions and path geometry;

• road speed limits - preferably, the system 100 does not select an alternate route that greatly reduces the speed values that are on the other roads, (example: if road A has a speed value of 80km/h and road B has 70km/h then an alternate route should not, wherever possible, be on roads with a speed values of 40 or 50km/h);

• availability of alternate routes with TMC paths - for example, if roads A and B have TMC points and paths in the database and alternate route giving guidance around a restriction or a TMC incident location should also be covered by TMC points and paths;

• school zones - for example, if roads A and B do not pass school zones then an alternate route should be considered that reflects the same condition to avoid, wherever possible, travel time restrictions;

• grade separations;

• load and size limitations - such as for routes that do not have vehicle load and limit restrictions (HV), any alternate route around any of the restrictions listed above must take into consideration the existence of HV restrictions on any alternate route and are not to be considered or can be considered without appropriate vehicle type restrictions being applied to the alternate route geometry;

• vehicle type limitations - such as for routes that do not have vehicle type (VT) limitations, any alternate route around any of the restrictions listed above must take into consideration the existence of VT restrictions on any alternate route and are not to be considered or can be considered with appropriate VT restrictions being applied to the alternate route geometry;

• possibility for temporary road closures - alternate routes should be avoided on roads that may be subject to temporary closures due to various reasons including weekend closures for market stalls and around stadiums where road closures occur for crowd control;

• traffic light configurations;

• road standard including form of way, lane count and turning lanes;

• existence speed calming devices including speed humps, chicanes, lane/road narrowing and roundabouts;

• possible congestion caused by the local environment (i.e. shopping precinct or "local traffic only" zones); and

• availability of other sign posted alternate routes.

Based on the path data and rules data, the map editing system 102 selects an optimal route with one or more interconnected paths adjacent to a selected node in the transportation network. The optimal route represents the combination of paths that allows traffic to negotiate past the selected node to reach a destination in a nominated direction of travel.

The paths included in the optimal route are selected on the basis that the combination of paths would enable traffic to negotiate past (either through or around the selected node) in the least travel time, or for the least actual distance travelled. This selection is also based on considerations of selecting paths with similar FRC values to avoid great differences in travel speed, which may not be desirable for travellers (e.g. a path with a FRC value of 5 would consider combinations of paths with a FRC value of 4 or 6, but not 1 or 10).

After the paths for the optimal route are selected, the map editing module controls updates the FRC values for the paths included in the optimal route. One advantage of this is that the map enhancing system 100 only needs to perform one processing step to identify the optimal combination of paths (i.e. the optimal route) for directing traffic around a node. By specifically coding this selection, the need for a navigational device to perform detailed processing of map data to identify the same combination of paths is reduced. This enables optimal alternative routes for traffic to negotiate around certain nodes to be identified much more quickly and efficiently.

The map enhancement system 100, under the control of the map editing module 102, performs a process 200 as shown in Figure 2. Process 200 begins at step 202 where the map editing module 102 accesses map data representing a transportation network, which includes path data and rules data as described above.

At step 204, the map editing module 102 selects a route including one or more of the paths in the transportation network. This selection is based on the constraints and features defined in the path data and rules data. The selection may be performed by human selection, or alternatively, but a computer algorithm that reviews the different combinations of paths relative to the selected node in order to identify the optimal path.

At step 206, the map editing module 102 adjusts the functional class of the paths selected as the optimal path.

At step 208, the map editing module 102 generates enhanced map data which, for example, consists of a modified version of the map data retrieved from the database including the changes to the FRC values. Alternatively, the enhanced map data may represent instructions to

update particular portions of the map data stored in the database 104. Process 200 ends after step 210.

The operation of the map enhancement system 100 can be better understood with reference to the following examples, where the diagrams include reference to the following codes: (where RC is abbreviated form of Functional Road Class or FRC)

• a Motorway - RC = 0

• major roads - RC = 1

• subsidiary roads - RC = 2

Other relevant codes not used in these diagrams include:

• minor roads - RC = 3

• minor suburban roads - RC = 6

• private roads - RC = 7 Example 1

In Figure 1, In the diagram above Rutledge Street [A] has a physical barrier such as median strip (Grade Separated Crossings) GEC prohibiting east & west bound traffic from making a right hand turn to West Parade [B]. In order for east & west bound traffic on Rutledge Street

[A] to access West Parade [B] the RC of Trelawney Street [Cl] and Clanalpine Street [Dl] are adjusted for all road elements required to give RC connectivity between Rutledge Street [A] and West Parade [B]. Connectivity between roads is thus achieved by changing the RC attribute to give the same or hierarchal connectivity between grade separated roads.

Example 2

Example 2 will be explained with reference to Figure 2 which uses the reference numerals listed at the dot points above.

In Figure 2 Rutledge Street [A] has a sign posted prohibition saying "No Right Turns" [NRT] prohibiting east and west bound traffic from making a right hand turn to West Parade [B]. In order for east and west bound traffic on Rutledge Street [A] to access West Parade [B] the RC of Betts Road [Cl] and Anthony Road [Dl] were all adjusted to give RC connectivity between Rutledge Street [A] and West Parade [B] via alternate routes along Betts Road [Cl] and West Parade [Dl].

Example 3

Example 3 will be explained with reference to Figure 3 which uses the reference numerals listed at the dot points above.

Figure 3 shows road Rutledge Street [A] has a sign posted restrictions (that relate to specific days of the week, times of day and vehicle type) on the exit ramp [Ramp] that apply to west bound traffic making a left hand exit followed by a left or right hand turn onto West Parade

[B]. In order for east bound traffic on Rutledge Street [A] to access West Parade [B] the RC of

Trelawney Street [Cl] and Clanalpine Road [Dl] are adjusted for all road elements required to give RC connectivity between Rutledge Street [A] and West Parade [B] for periods when the ramp is closed.

Example 4

Example 4 will be explained with reference to Figure 4 which uses the reference numerals listed at the dot points above.

Figure 4 shows Rutledge Street [A] has a sign posted time of day and day of week with or without vehicle type restriction on the exit ramp [Ramp] prohibiting west bound traffic from making a left hand exit followed by a left or right hand to West Parade [B]. Lane guidance information [Lane] based number and type of lanes are coded as well to give appropriate guidance advice depending on the time dependant restrictions on the exit ramp [Ramp]. In order for east bound traffic on Rutledge Street [A] to access West Parade [B] the RC of James Street [Cl] and Greening Road [Dl] are adjusted for all road elements required to give RC connectivity between Rutledge Street [A] and West Parade [B] for periods when the ramp is closed. Lane guidance coding provides information to maintain current heading to the alternate route.

Example 5

The database image in Figure 5 shows the relationship between land information and restrictions based on vehicle types and physical separations.

In the diagram above road Rutledge Street [A] has traffic Messaging channel information [Tl, T2, T3]. A traffic incident is reported at location [T2] recommending west bound traffic do not make a right hand turn to West Parade [B]. Alternate routing advice then plans a route to avoid the traffic incident at location [T2] by taking the exit ramp [Ramp] at location [Tl] followed by guidance along Elsie Road [Dl] and Smith Street [Cl] to West Parade [B]. In

order for west bound traffic on Rutledge Street [A] to access West Parade [B] the RC of Smith Street [Cl] and Elsie Road [Dl] are adjusted for all road elements required to give RC connectivity between Rutledge Street [A] and West Parade [B] when coding for incident reporting.

Example 6

In determining what FRC value a path (or road) needs to change to, a closed hierarchical road network must be maintained. All road elements making the connection between 2 roads that have a restriction prohibiting a turn in any direction from road A to Road B must be upgraded to match the lowest FRC value of roads A and B.

Figures 8 is a map of a portion of the road network in a nominated region. Pacific highway 802 has an initial FRC value of 2. Mowbray Road is made up of paths 804 and 805 (delimited by various junction points) and each path corresponding to Mowbray Road has an initial FRC value of 4. Orchard Road 806 has an initial FRC value of 6. Nelson Street has an initial FRC value of 6. There is a sign posted "No Right Turn" from Mowbray Road 804 east bound into the Pacific Highway 802 at junction "A". In this example, it is assumed that a driver travelling east bound along Mowbray Road 804 intends to turn onto Pacific Highway 802 to head south and prefers to travel along a main road. In Figure 8, the intended travel direction is shown using dotted arrows.

Based on the path data and rules data for paths in the geographic region shown in Figure 8, the map editing module 102 selects Orchard Road 806 and Nelson Street 808 as a suitable alternative route for directing traffic onto Pacific Highway 802 to continue travelling south bound. This selection is based on the consideration of the total distance travelled by the combination of paths 806 and 808 in order for traffic to reach Pacific Highway 802. After selecting various combinations of paths which provide the least travel distance for routing eastbound traffic on Mowbray Road 804 and 805 to head southbound on Pacific Highway 802, a further selection is performed on the basis of other path attributes (defined by the path data).

Preferably, this further selection involves selecting paths having an initial FRC value that is close to the FRC value of the path on which the driver is originally travelling on (so as to minimise difference in travel speed along the selected paths), and also based on consideration of any other factors which may affect the speed (e.g. the presence of lower "school zone" speed limit during that time of the day, or the presence of a shopping centre with heavy pedestrian traffic).

The combination of paths 804, 805, 806 and 808 are selected by the map editing module 102, and the FRC values for these paths need to be adjusted to indicate preference for this combination of paths as an alternative route for traffic to negotiate the turn restriction at junction A. To allow appropriate route planning Nelson Street 808 and Orchard Road 806 have been upgraded from a FRC=6 to FRC=4 to match the lowest FRC value of 4 for these combination paths (i.e. the FRC value for Mowbray Road 804 and 805) forming a closed network giving access to Pacific Highway for south bound routes.

Example 7

In determining what FRC value a path (or road) needs to change to, a closed hierarchical road network must be maintained. For all road elements making the connection between 2 roads that have a physical restriction (median strip) at the junction ruling out a right hand turn from road A to Road B all other road elements providing an alternate route must be upgraded to match the lowest FRC value of roads A and B.

Figures 9 is a map of a portion of the road network in a nominated region. West Parade is made up of paths 902 and 904 (delimited by various junction points) and each path corresponding to West Parade has an initial FRC value of 4. Rutledge Street has an initial FRC value of 4. Clanalpine Street 906 and Trelawney Street 908 both have an initial FRC value of 4. In this example, it is assumed that a driver travelling southbound along West Parade 902 intends to turn right onto Rutledge Street 910 to head westbound. There is a sign posted "No Right Turn" at junction "B". There is a physical barrier positioned in a manner to prohibit a right hand turn from the West Parade slip road into Rutledge Street. Similar to Example 6, the map editing module 102 selects the combination of paths 902, 904, 906 and 908 to be the most suitable path based on the path data and rules data for the paths in the geographic region shown in Figure 9. To allow appropriate route planning, the FRC values for Clanalpine Street 906 and Trelawney Streets 908 have been upgraded from a FRC=6 to FRC=4 to match the lowest FRC value of the combination 902, 904, 906, 908 (i.e. corresponding to the FRC value for West Parade) forming a closed network giving access to Rutledge Street east bound.

Example 8

In determining what FRC value a path (or road) needs to change to, a closed hierarchical road network must be maintained. All road elements making the connection between 2 roads that have a grade separated physical restriction (bridge or overpass) ruling out a turn from road A to Road B must be upgraded to match the lowest FRC value of roads A and B. Referring to

Figure 9, there is a physical grade separation between West Parade and Rutledge St prohibiting access. To allow appropriate route planning Clanalpine and Trelawney Streets have been upgraded from a FRC=6 to FRC=4 to match the lowest FRC value of 4 on West Parade forming a closed network giving access from Rutledge Street to West Parade.

Modifications and improvements to the invention will be readily apparent to those skilled in the art. Such modifications and improvements are intended to be within the scope of this invention.

The word 'comprising' and forms of the word 'comprising' as used in this description and in the claims does not limit the invention claimed to exclude any variants or additions.