A trend that has been developing in Europe and is just beginning here in the US, is 20 mph streets. Typically, 25 MPH is the default minimum – often reserved for residential roads, but based largely on the design speed that the roadway was designed for. Somerset, MD, a small lovely residential hamlet in Montgomery County, has made a policy decision to reduce the speed limit for the entire town to 20 MPH.
This decision was not an engineering one (which typically deals with only the safety of drivers that are already pretty safe wrapped up in a 3000 lb steel box). Rather, it was a decision based on planning for slower roads and roads that are safer for all users (children, joggers, cyclists, etc.).
Some of the the positives and negatives of a slower Main Street are:
· Slower speeds making walking more comfortable for pedestrians.
· Slower speeds are better for bikers (speed differential between cars and bike is a main factor in bicycling level of comfort and broadening its appeal to more users.
· A pedestrian getting hit at 25 mph has 4-fold higher likelihood of dyeing than at 20 mph.
· Slower drivers are more apt to see the types of businesses that line Main Street.
· There is simply no engineering reason to allow/encourage 25mph speeds on Main Street, but there are certainly economic and safety reasons for lowering the speed limit.
· A driver will need an extra 23 seconds to travel the main retail stretch from MD 216 to US 1.
That’s it. On the surface, relying on planning and policy, rather than what a roadway could handle, sure seems to be a better way for towns to assign speed limits.