To provide a dedicated measure for quickly and accurately measuring a radius of curvature, which enables estimation of a traveling velocity via a calculation formula based on the relationship between a road face and a tire friction factor by measuring the radius curvature of a cornering trace impressed circularly on the road face by the friction between a tire of an automobile and the road face if the automobile travels beyond the limit of centrifugal force.

The limit velocity measurement measure for instantaneously determining an accurate impression velocity in the field from the cornering trace impressed on a road is provided with a measurement measure part, a limit velocity conversion table attached to the back face of a winding type housing case for showing conversions about a cornering trace impression velocity, which is calculated by a radius of curvature calculation method and a limit velocity calculation method based on the friction factor on the road face and the radius of curvature, and the winding type housing case allowing easy storage and portability. The measurement measure part has a long measure having fixing pins at both ends for preventing displacement during measurement and for easily making the measure fixed straight on the road face, and a short scale, whose rotation is controlled by engagement of a projection part using a steel ball for crossing the long measure at right angles.