The next causal factor addressed in this series is speed, which is a key risk factor in roadway accident injuries because it impacts the likelihood of a crash and generally increases the magnitude of the injuries resulting from crashes. Speed limits are established to maintain roadway safety; however, based on volatile conditions at a given time, there may be a need to recognize that a reduced speed is more suitable. Colorado statute explains that drivers must travel at a speed that is “reasonable and prudent” under the circumstances. Examples may include inclement weather, excessive traffic, or while traveling through a detour.
In wealthier countries, speeding is attributed to about 1/3 of roadway fatalities. Meanwhile, in poorer nations, this percentage rises to approximately 1/2. When traveling at a higher rate of speed, there is a corresponding reduction in available reaction time. The Insurance Institute for Highway Safety reported that in the U.S. in 2015, excessive speed caused roughly 27% of vehicle fatalities. The rates for fatal accidents caused by speeding were reported by roadway type as follows:
- Minor roads: Rate of 32%
- Interstates and freeways: Rate of 30%
- Other major roads: Rate of 24%
- The number of traffic fatalities on roads with a posted speed limit of less than 55 mph was evenly split with those occurring on roads where the limit exceeded 55 mph.
There are a host of methods employed to manage vehicle speed, with the posting of speed limits obviously being the most common. Data suggests that merely posting a speed limit, or posting a reduced speed limit on an existing stretch of roadway, has a good short-term effect. Over time, this effectiveness declines if the limits are not enforced in a consistently visible manner. Speed cameras have been increasingly used in many states and are likely the most cost-effective of the alternatives. Creating roadway environments that result in lower flows of traffic are effective in reducing collisions. Some success has also been documented by the “segregation” of traffic, which encourages drivers to use routes that are either lower or higher speed, such as “express” lanes. It is always critical that speed differences (disparities) are minimized in traffic flows.
Differentials in Speed
Vehicles traveling in the same flow of traffic should be doing so at low-speed differentials. The speed differential is calculated by determining the range of all the vehicles within a specific stream of traffic. When large variations exist among vehicles in the same traffic stream, there are likely more occurrences of abrupt braking, vehicle lane changes, and other such maneuvers.
Physical Traffic Control Options
Several methods of calming traffic have shown to reduce the frequency of accidents. These include physical roadway changes geared to lower speeds including roundabouts (circles), speed bumps, and rumble strip installation. A high risk exists for accidents when roadways have transitions in the speed of travel, such as ramps where vehicles are exiting interstates. In these areas where a change of speed is necessary, there tend to be signs or signals that give drivers a warning so that their actions are less reactionary. In recent years, commercial vehicles (trucks) have begun to have speed limitations already programmed into the vehicle's control system.
Speeding in Work Zones in Colorado
Zones of roadway where construction activity is underway are areas where reductions in speed are very critical. Local posted signage and officer speed enforcement is typically heaviest along these stretches, as are penalties for violators. Generally, the monetary penalties for those who violate are doubled. The Colorado Department of Transportation (CDOT) posts appropriate signs and signals at least four hours prior to any construction work commencing.
Colorado Speeding-Related Laws
The prima facie or “on the face of it” speed limits in the state are generally:
- 20 mph for narrow stretches of roadway or on curvy mountain roads
- 25 mph in commercial or business areas
- 30 mph in residential areas
- 40 mph on mountain roadways
The state allows cities to implement ordinances that establish speed limits within their jurisdictions; however, the maximum lawful limit is 65 mph on open highways and 75 mph on interstate highways.