Senate Bill 2356 as amended essentially raises the speed limit of cars and trucks on the rural Illinois interstate highway system to 70 miles per hour and has been sent to the governor. It should be recognized that the state of Illinois is in a unique location adjacent to Lake Michigan, which results in greater usage of our interstate highways by trucks than in adjoining states. Thus, the proposed raising of the truck speed limit to 70 mph will create problems unique to Illinois.
Most highway and traffic engineers have a problem with the higher speed for trucks. There is a direct relationship between speed and severity of injuries in a collision. Higher truck speed will have a price in terms of human grief, and we hope the governor is aware of that.
It is well known that the Illinois State Police who enforce the speed limit generally allow a speed tolerance to make certain the tickets they issue are upheld in court. This tolerance of 7 to 10 mph over the posted limit will allow trucks to travel at 77 to 80 mph with impunity. At those speeds so much depends upon driver reaction time to avoid collisions.
There are some rural locations where the highway geometry will not safely accommodate this higher speed. IDOT should study the entire system to identify those locations and set proper limits regardless of county.
We encourage IDOT to evaluate the interstate highway system to determine if any changes are needed prior to posting a higher speed limit. If enacted, annual speed surveys and accident analysis reports should be made available to the legislature and public to determine if the small incremental trucker time saving, which is the intent of this law, is worth the risk to all motorists.
Carl F. Kowalski
Retired Cook County superintendent of highways
George T. March
Retired IDOT district engineer