Updated: May 14, 2014 6:46AM
Interstate highway speed limits that are too low are dangerous, and the speed limits on Chicago-area tollways such as I-88, I-294 and I-355 fit this description.
Transportation engineers worldwide almost unanimously advocate posting speed limits based on what’s known as the free-flowing, 85th-percentile speed — the speed below which 85 percent of vehicles actually travel when not impeded by traffic or heavy visible enforcement.
The Institute of Transportation Engineers says, “drivers traveling significantly faster or slower than the 85th percentile speed are at a greater risk of being in a crash.”
The free-flowing 85th percentile speed on Chicago-area interstates is estimated by experts at the National Motorists Association to be at or above the new state speed limit of 70 mph in most areas. This is obvious to many area commuters.
In view of the danger of driving 55 mph, far below the average speed on area expressways and tollways, the Illinois State Toll Highway Authority is endangering our children and others who obey the speed limit.
Former Illinois chapter
coordinator and life member,
National Motorists Association