This invention is concerned with a highway safety barrier preferably made of precast concrete, mainly as a traffic divider barrier, and accessorily as a side barrier, a further variation being a side barrier for bridges.

Prior concrete safety barriers have mostly been of the New Jersey style. They generally comprise elongated blocks that are laid on the ground end-to-end and are generally hooked to each other by any of a number of arrangements, such as a tongue-and-groove joint. The New Jersey barriers are usually tapered from the bottom upwards, and more usually they have a bell-shaped profile.

One of the aims of highway safety barriers as priorly known is to laterally contain a vehicle that has deflected from its path, while allowing it to proceed forward in sliding contact with the barrier until it comes to a stop or is steered back to its running path again. However, this ideal performance has a good chance of being achieved only in case of a hit at a slow speed and with a very small angle of incidence. In many cases, where the speed is high and the angle of incidence is appreciable, what actually happens is that the forward corner of the vehicle, obliquely hitting the barrier, is strongly braked by the deformation and the friction, while the vehicle tail, still propelled by the residual momentum, swings forward in a so-called "about-face", the vehicle finally coming to rest, often in a transverse position. Moreover, it sometimes happens that, in case of a particularly forceful hit, the vehicle is upturned and jumps over the barrier into the adjacent roadway or precipice, as the case may be.

Such collisions of vehicles against the barriuer often cause death and injury not only for the passengers in the deflected vehicles, but also for other persons that are fortuitously involved in the accident because their vehicles are unable to avoid crashing into the obstacle suddenly placed in their paths. Not infrequently, this circumstance leads to a pile-up of several vehicles, and, as well known, deaths and invalidities due to this kind of accidents are counted in thousands or tens of thousands every year.

The main object of this invention is therefore to provide a highway safety barrier which will reduce the above drawbacks of prior barriers, and which, more particularly, will reduce the number of about-faces and of sudden stops of the deflected vehicles, and which will tend to lead the vehicles back onto the roadway.

Another object of the invention is to eliminate or reduce the number of vehicles being upturned and jumping over the barrier.

A further object is to implement the above barrier so that its installation, main¬ tenance and repair may be quick and easy.

The above and other objects and advantages, such as will appear from the following disclosure, are achieved by the invention with a highway safety barrier having the novel features set out in claim 1, while the dependent claims recite other advantageous features of the invention.

The invention will now be described in more detail with reference to a few preferred, though non-exclusive, embodiments, which are shown by way of example in the attached drawings, wherein:

Fig. 1 is a view in side elevation, partly broken away, of a portion of a safety barrier according to a first preferred embodiment of the invention, showing a traffic divider safety barrier against deflections of vehicles from their proper running direction;

Fig. 2 is a view in transverse cross-section for the first preferred embodiment of the invention, showing a traffic divider safety barrier, which is exposed to the most dangerous hits;

Fig. 3 is an enlarged view in cross-section of a detail of Fig. 2;

Figs. 4, 5, 6 e 7 are diagrammatical plan views showing the development of a typical impact of a vehicle against the barrier of the invention, in its preferred embodiment as a traffic divider, and therefore placed at the midline of the road;

Fig. 8 is a view in transverse cross-section of a second embodiment of the invention,

showing a side safety barrier acting against deflections of vehicles toward the outside of the roadway;

Fig. 9 is a view in transverse cross-section of a side safety barrier, in a variation intended for bridges.

With reference to Figs. 1 and 2, a traffic divider safety barrier according to the invention comprises a plurality of identical, precast, monolithic blocks such as 10, which are arranged in a row along the midline of a roadway 26. Each monolithic block 10 has a uniform transverse profile, is made of conventionally reinforced concrete (not shown), and comprises two inclined, symmetrical, elongated running boards 12', 12", supported on one or more back buttresses 14, and an elongated body 16 which rises in a subvertical direction from running boards 12', 12" over its entire length, and which has lateral surfaces inclined toward the running boards. The low sides of running boards 12', 12" and buttresses 14 rest on continuous foundation slabs 20, 22, so that the outside edges of the running boards are on a level with the edge of roadways 26', 26".

Buttresses 14 may be merged into a single continuous body as shown on Figs. 1 and 2, but they may be isolated supports, e.g. at the opposite ends of the monolithic block.

The running boards are preferably about 1 -meter wide, and their slope to a horizontal plane is in the range 25% to 35%, and preferably is about 30%, although it is envisaged that even larger or smaller slopes may be useful, in a range 15% to 40%.

The length of a monolithic block is in the range 2.5 to 3.0 meters. Body 16 preferably extends for a height of about 1 meter, and the inclination of its side surface 18', 18" is in the range of 5° to 15° with respect to a vertical direction, preferably about 10°, whereby the running boards and surface 18 form an angle that is nearly square but is slightly obtuse, for instance about 100°. Fig. 2 also shows the profile 27 of a car hitting the barrier.

Each monolithic block 10 has slots 28, 30, 32, 36, at its opposite ends. The slots are located at the top of body 16, as well as at the low sides of running boards 12', 12". The slots all have the shape of narrow cavities which are respectively open at the top and toward the opposite ends of the monolithic block. Preferably, the slots have respective transverse cross-sections which narrow down toward the top, i.e. toward the upward opening of each slot, as shown on Fig. 3. Slots 28, 30 are preferably vertical, while slots 32, 36 in the longitudinal cross-section, are respectively inclined in opposite directions. Each slot is typically about 15 cm long, 10 cm high, and 2 cm wide, although these dimensions are not critical and are changeable within wide limits.

Each slot faces, in the joining section, similar slots in the adjacent elements, which all have a length of about 15 cm and a height of about 10 cm.

The traffic divider barrier is built by laying down a plurality of identical monolithic blocks 10 in succession on foundation slabs 20, 22, in mutual alignment and in end contact with each other. The individual blocks may be fastened to the slabs by conventional means such as tie rods (not shown). Adjacent blocks are then joined to one another by inserting a respective shear key such as 40, 42, 44 in each pair of contiguous slots at the joints. Each shear key is a rectangular metal blade, of a size such that it will extend over the greater part of the overall length of both contiguous slots, and that it will be entirely contained within the slots without sticking out at the top, as shown also on Fig. 3. The slots are then filled with a non-shrinking mortar or with a colloidal grout (not shown). The tapering section of the slots insures that the shear key is well fastened, and therefore that the joint is stable.

The above described traffic-dividing barrier, shown on Fig. 2, is the embodiment offering the maximum advantages of the invention, because the most dangerous collisions actually take place against the traffic-dividing barrier, since the speed of the vehicles is usually much higher in the fast lane bordering the barrier.

With reference to Figs. 4, 5, 6 and 7, in an average situation, when a deflecting vehicle 50 obliquely approaches the above described traffic-divider barrier, its

outside front wheel will initially run over the running board 12 (Fig. 4), and then proceed until it hits the subvertical body 16 of the barrier, the car body being consequently deformed. By static effect, the vehicle will turn in plan toward the barrier, until its side rests against body 18 in full contact (Fig. 6), while the vehicle pursues its longitudinal motion in sliding contact with the barrier. A great part of the initial energy will be dissipated this way. When the dissipated energy is such that the force mantaining the vehicle in contact with the barrier becomes smaller than the transverse component of its weight, the vehicle will move away from the barrier and fall back onto the roadway almost automatically, due to the slope of the running board (Fig. 7). The vehicle will not usually be abruptly stopped with consequent damages.

The above described traffic-divider barrier will also make it practically impossible for a a vehicle to be overturned and to jump over the barrier, due to the combined effect of both the slope of the running board and the inclination of wall 16, which both will oppose any upward force.

As a person skilled in the art will appreciate, shear keys 40, 42 are able to absorb shear stresses acting transversely and horizontally to the barrier, while shear keys 44 will also absorb rotational stresses.

The second embodiment of the invention, which is the lateral barrier, is a modi- fication of the traffic-divider barrier, shown on Fig. 8 in its common form, and on Fig. 9 showing its use on bridges. It is intended for installation at the outer border of the roadway or on a bridge 52. Here the monolithic block has a sloping running board 12 with a back buttress 14 and a subvertical wall 16 having an inclined lateral surface, and slots provided with shear keys such as 54, 56. Since it is intended to react to vehicles deflected outwardly from the highway or motorway, it has a structure with a longitudinal profile similar to the traffic- divider barrier only on the side toward the roadway, and is therefore asymmetrical. The block of Fig. 9 (intended for bridges) is fastened to the bridge 52 by tierods 58, and its buttress 14 is provided with a vertical wing 60 which laterally frames the bridge.

The lateral highway safety barrier comprises a series of identical, precast, elongated blocks (10) that are laid in a row along the outer border of the roadway (26 ¹ ). The blocks try to contain within the road any vehicles which tend to depart from it. Each block comprises, on the side toward the roadway, a longitudinal board transversely sloping toward the roadway and a rectangular body (16) having a surface (18) that is slightly inclined with respect to the barrier axis.

Several other changes may obviously be made to the examples described above. In particular, the running board might have, rather than a substantially flat sloping surface, a convex or a concave surface, provided that it slopes down toward the level of the roadway. Also, the surface of the running board might be ribbed or stepped longitudinally, in order to provide an audible signal to the driver of the deflected vehicle, in a way known to persons skilled in the art; accordingly, the expression "flat surface", as used in this disclosure and in the claims, should be understood as referring to the average, overall look of the surface, independently of any small bumps as stated above. The running board, for the same purpose of providing an audible warning, could also be painted with a noisy paint as known in the field of road construction.

The joints between the barrier blocks could also be differently made, e.g. as tongue- and-groove joints, as known in the art. Also, the inclination of subvertical wall 18 might be dispensed with, though not the slope of the barrier board. The concrete used for the barrier might be replaced with another material, including metal.