The Institute of Transportation Engineers is an international agency that defines traffic calming as changes in street alignment, installation of barriers, and other physical measures to reduce traffic speeds and cut-through volumes in the interest of street safety, livability, and other public purposes.
Traffic calming is typically classified as either speed or volume control. The City of Helena will not typically implement volume control retroactively, but more information this type of traffic calming can be found here.
The City has implemented speed control traffic calming in numerous locations. This type can be further classified into three different sub-types: horizontal measures, vertical measures, and narrowings.
Horizontal measures force vehicles to slow down before safely navigating around them. Curves and angle points are introduced within the road’s alignment to decrease the driver’s comfort level. The decrease in driver comfort results in the driver slowing down. Realigned intersections, roundabouts, and alternating angled parking are some of the examples of horizontal measures used within the City.
Vertical measures force vehicles to slow down before driving over them. Speed humps are the standard vertical measure most often used in cities. It should be noted that speed “bumps” are not allowed within the City’s public streets. Speed “bumps” are more abrupt and are typically used in the parking lots of large retail shops (such as Target, Costco, and shopping malls). Speed bumps do too much damage to vehicles, and more importantly, impact fire trucks and ambulances too severely.
Narrowings alter driving habits by confining the comfort zone of drivers. The more “cramped” a driver feels, the more they will slow down. Narrowing streets also brings the added benefit of narrowed crossings for pedestrians. The narrow street crossings will lessen the time a pedestrian needs to spend within the roadway. Curb bulbouts are the typical narrowings used in numerous locations across the City. Below is an example of a bulbout installed in downtown Helena.