UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Redirection effectiveness of roadside curbs Lafond, Nadine


Curbs are commonly used along urban streets, in channelised intersections, and along medians and ramps. One of its purposes is to protect pedestrians. The protection offered by a curb is measured by its ability to redirect errant vehicles. A curb redirection effectiveness depends upon the speed and the angle of impact of a vehicle, the height of the curb, the vehicle mass, and the tire radius. The effectiveness is also influenced by other factors such as the coefficient of friction between the tire and the curb, the tire pressure, and the geometric design of the curb. The redirection ability of a 152 mm high curb of type C design from the AASHTO Manual was investigated during 28 full scale tests. Six vehicles, of a mass between 675 and 1750 kg, impacted the curb at a speed varying from 6 to 34 km/h, at angles of 5°, 10°, or 15°. Four tests were performed to evaluate scrubbing conditions and a 90° impact. Mass was added to some vehicles to measure the influence of the mass without modifying vehicle dimension and properties. It was found that a type C curb does not provide an appropriate protection to pedestrians since it can easily be crossed when the component of the velocity normal to the curb exceeds 2 km/h. Redirection was not achieved in any of the tests performed at an impact angle of 15°. According to the tested data, the probability that a vehicle is not redirected by the curb starts at an impact speed of 10 km/h and reaches 100% at a speed of 40 km/h when approaching the curb at a 5° angle. An equation relating redirection speed to the impact angle, the curb height, and the studied vehicle parameters, was validated. A safe curb height of 205 mm is suggested to substantially improve the curb's ability to redirect an errant vehicle hitting a curb at a shallow angle, up to a normal speed of 4.7 km/h.

Item Media

Item Citations and Data


For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.