Setting speed limits 101

Everyone wants a speed limit in front of their house but not in front of everyone else’s! This statement certainly seems to hold true for Franklin County. A number of recent requests to reduce speed limits at various locations further upholds the perception, if not the reality, that most drivers are guilty of speeding.

New York State Vehicle and Traffic Law (VTL) gives the authority to set speed limits to villages and cities. Speed limits in villages and cities are considered to be “area speed limits”, and, except for New York City, VTL prohibits area speed limits to be less than 30 mph. Thus, no village can set a speed limit less than 30 mph. Towns with populations of 50,000 or more may also set their own speed limits but no towns in Franklin County qualify. So, basically, in Franklin County, authority for setting all speed limits, except for our villages which cannot be less than 30 mph, rests with the New York state Department of Transportation.

DOT also has exclusive authority to set speed limits on all state highways, regardless of where they are located. To change speed limits on any road other than on state highways, the town board and the county highway superintendent must file a joint request with the Regional Office of the DOT (Watertown for Clinton, Franklin, St. Lawrence, Jefferson and Lewis counties) to conduct a speed limit study.

A properly set, properly signed speed limit can promote safe and orderly flow of traffic. An improperly signed speed limit may be difficult for police to enforce, and an unrealistically low or high speed limit can lead to disrespect of speed limits in general. Posted speed limits have been shown to have little effect on the overall speed of traffic, but appropriate set speed limits provide a sound basis for enforcement. Therefore, any speed limit should be enacted only with a proper engineering study. That’s why this function rests with the professional traffic engineers at DOT.

Engineering studies for speed limits most always include a free-flowing speed study to determine the “85th percentile”, which is the speed at or below which 85 percent of free-flowing vehicles are traveling. After the 85th percentile is determined, speed limits are generally set to within 5 mph of this value. There can be other factors involved, such as crash frequency that is determined to be speed-related, pedestrians, bicyclist activity, but in general, the driving factor is the 85th percentile.

With the above as background, let’s look at the Brainairdsville Road (county Route 24) as an example. For years, there has been an effort by some residents and even the Town of Bellmont, to try to keep speeds under control on this road. However, when we build our roads straight and smooth, with wide shoulders and without a concentrated residential population residing along the road, drivers do not perceive the necessity to even travel at the statutory state speed limit of 55 mph, let alone anything lower.

Should the Town of Bellmont proceed with a request to reduce the speed limit on this rural road, it will be interesting to see how DOT reacts. I would offer that the 85th percentile will be 60 mph or higher. If this holds true, it would be very unusual that DOT would approve a lesser speed than the existing 55 mph. This may not be what residents want to hear, but this is the reality of setting realistic speed limits.

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