By Dom Nozzi
Regarding speed humps…
I am possibly the biggest advocate in South Carolina for using traffic calming devices on streets, as I believe slowing cars is one of the most important things we can do in cities for better safety, quality of life, reduction in low-value motor vehicle trips, and noise reduction.
Speed humps, however, are an exceptionally problematic tool for slowing cars. On the list of bad ideas for slowing cars, speed limit signs are at top of the list for being the worst. Stop signs are about as bad. And humps are #3 for being a bad tool.
Here is why humps are a bad idea:
They punish motorists even if the motorist is driving fairly slowly.
They can damage vehicles.
They create noise pollution for neighborhoods.
They create problems for emergency response vehicles.
They are annoying for cyclists.
When spaced improperly, they promote “jackrabbit” driving (ie, frequent slowing and speeding between humps).
An important reason why many cities such as Greenville use (or overuse) humps so often (there are way too many humps in Greenville) is that they are very quick and low-cost to install. Which makes them an easy way for elected officials to satisfy neighbors concerned about speeding vehicles.
However, the best way, by far, to slow motor vehicles is not to use “vertical” interventions such as humps, but to use “horizontal” interventions. Examples of horizontal interventions include:
1. Road diets, where excessive street lanes are removed. The most common diet is going from 4 lanes to 3.
2. Landscaped or hard-surface bulb-outs (usually used to frame on-street parking or create a mid-block pedestrian crossing). Many bulb-outs are admirably used on Greenville’s Main Street. Ideally, this “pinching down” the width of the street creates a one-lane-wide pinch point that obligates motorists to “give-way” when a motor vehicle approaches in the opposing direction.
3. Chicanes, which are a form of bulb-out that obligates motorists to move in a slower, weaving, more attentive pattern.
4. Traffic circles and roundabouts.
5. Installing on-street parking on streets without such parking. Again, this narrowing of street width works best when a “give-way” street is created.
6. Installing formally-aligned street trees abutting the street to create a sense of enclosure and human scale.
Each of these horizontal interventions is much more conducive to bicycling and emergency response vehicles than vertical interventions such as humps. They are also much better at creating a safe environment for walking. As well as created the much-needed human scale and sense of place that is lost when we oversize streets and intersections.
On my list of top priorities for Greenville to become a better city, traffic calming is near the top of the list. But calming needs, again, to be achieved with horizontal rather than vertical interventions.