In 1906, a small town in New Jersey officially and successfully installed the first recorded speed bump. The town of Chatham used the ‘speed reducers’ to alert cars to pedestrians using crosswalks. On the day they were tested, hundreds of residents gathered around the bumps to watch the ‘machines’ drive across them. The bumps, which were 5 inches high and made of rock and clay, gave the first motorists to traverse them quite a rude surprise when his car shot up several feet. This solicited a loud cheer of approval from all those watching and proved that the speed bumps were in fact effective. We should all take a moment to thank modern suspension for being able to handle speed bumps a little better than Fords model A’s, C’s, and F’s.
Today the term speed bump is often used to refer to a family of vertical deflection devices. Within the family there are variations of the speed bump, a hump, and a cushion.
Identifying the Vertical Deflection Devices
Speed bumps are the most commonly used form of vertical deflection devices. Due to speed bumps height (3-4 inches) and their width (usually 1 foot), they are designed to slow vehicles down to about 5 mph, which makes them ideal for parking lots. The City of Bellevue does not install this type of device.
Speed humps, originating in England, are more convenient for residential roads where the intent is to slow cars down to about 15-20 mph. They tend to rise up to about 3-4 inches but do so over a much broader distance. They are usually 12-22 feet in length and span both lanes. Speed humps were designed in the 1970’s as an alternative to speed bumps so that emergency response vehicles response time wouldn’t be as impacted when responding to an accident. The City of Bellevue uses speed humps that are 22 feet in length on emergency response routes, used for raised crosswalks, in areas with transit routes, and on roadways have that have higher traffic volumes. Wondering why speed humps are not labeled as speed humps (versus speed bumps) in the City of Bellevue? Well, it’s a commonly stolen sign.
Bellevue also uses what is called a split speed hump. This is where the speed hump is split into two sections. Each section crosses the entire lane but they are placed several yards down the street from each other. This allows emergency response vehicles to navigate between them instead of over them.
A speed cushion is similar to a speed hump but instead of being a single bar across all travel lanes it is cut into multiple sections. The middle section is six feet wide with one foot slots between the outer sections. This allows vehicles with wider axles such as emergency response vehicles to drive through the slots without having to slow down.
Sleeping Policeman: United Kingdom, Judder Bar: New Zealand, Band of Breaking: Mexico