As part of ongoing efforts to curb speeding in our neighbourhoods, speed humps were recently installed on Liard Street. The new speed bumps are 80 mm in height as is standard throughout the City of Ottawa.
Here is the rationale for the general speed hump specs that I received from the Area Traffic Management (ATM) group:
“The speed hump design(s) that we use on City of Ottawa roads are designs that have been developed/adopted by the Transportation Association of Canada (TAC). The 80 mm height is actually the maximum height that is recommended for these profiles (sinusoidal and flat-top). The reason that we try to adhere to these approved designs is largely due to the desire to minimize our exposure to liability. It would not be responsible for staff to effect arbitrary changes to a tested and approved design. These types of changes could also expose the City to liability claims if collisions or damage to vehicles were to be involved. “
Previously, Liard Street had 76 mm temporary speed humps.
Although the permanent speed humps are only slightly taller than the temporary ones, they will feel different. The Temporary Speed Humps (manufactured by Traffic Logix) are constructed with rubber and they sit on top of the asphalt (therefore there is a small lip at the transition from the road to the speed hump) whereas the permanent speed humps are integrated into the road using the same materials and there is no transition. This might explain why there is a perception that the temporary speed humps were taller and more effective; however, the new speed bumps do meet the safety regulations and should discourage drivers from exceeding 40 km/hr.