White car driving quickly

How Speed Limits are Set & Why That Matters

When you are driving, you probably follow all speed limits, whether they are posted or not. Most drivers do the same without knowing why those speed limits are chosen in the first place. Although you probably knew that speed limits are not all arbitrary or random, you might not know how much work goes into selecting a speed limit or how driving in excess of those carefully selected limits can increase a driver’s liability in case of a car accident.

Calculating Different Types of Speed Limits

According to the Federal Highway Administration (FHA), speed limits are set and enforced by local and state authorities. For the most part, though, states and counties follow the suggestions of the FHA, which is part of the U.S. Department of Transportation.

There are three categories of speed limits:

  • Statutory: A statutory speed limit is set by state laws and is expected to be known and followed by all drivers, regardless of whether or not there are signs around that display those limits. Common statutory speed limits are 25 mph in residential and school areas, 55 mph on highways, and 70 mph on interstates.
  • Posted or regulatory: A posted speed limit is specifically determined for a stretch of road and is shown to drivers through posted signs, street decals, etc. Posted speed limits can vary from road to road, which we will discuss in more detail in the next section.
  • Special: A special speed limit is used for certain situations that are usually temporary. Roadwork, inclement weather, and special public events are common reasons for special speed limits. Drivers will usually be notified about a special speed limit through obvious signage, like orange signs near construction zones or large roadside LED displays.

How Speed Limits are Established

Statutory and special speed limits are usually arbitrary and unchanging from one state or situation to another. As mentioned, posted speed limits are those that can change considerably because each is carefully calculated and established by state or local civil engineers.

Civil and traffic engineers consider a few factors when calculating a posted speed limit:

  • Prevailing speed, which is the average speed driven among 85% of the drivers using the road.
  • Design of the road, including its curvature, lane count, width, etc.
  • Environment around the road like rocky cliffs or dense trees.
  • Expected or usual traffic conditions like how many drivers use the road in 24 hours.
  • Pedestrian and bicycle traffic typical for the road or region.
  • History of crashes on the road if any.

Speeding Raises Liability

The FHA reports that about 33% of all fatal car accidents involve a driver who is speeding. Additionally, 40% of speeding drivers who caused a fatal accident were also intoxicated.

With these statistics in mind and the fact that speed limits are carefully set to reduce the chances of an accident, a driver who intentionally speeds will likely increase their liability if there is a car accident. Attorneys who represent the injured will need to look for evidence that the other driver was speeding, which could include traffic cams, police reports, eyewitness statements, and photographs that show tire marks on the asphalt. The goal is to increase the speeding driver’s liability as much as possible so the injured claimant can get as much compensation as possible.

In a car accident in Chicago? The attorneys of McHargue & Jones, LLC would like to hear from you to see if we can help you pursue compensation from the speeding driver who hit you. Contact our firm now to ask for a free consultation.

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