Article Contributed on: 9/11/2008 2:04:58 PM
The Colorado Department of Transportation (CDOT) raised the speed limit Sept. 11 on I-225 between I-25 and Parker Road. Following a traffic engineering analysis as required by state law, CDOT determined that an increase in the speed limit from 55 miles per hour (mph) to 65 mph is the appropriate and safe speed limit for the highway's current condition
"Similar to the stretch of I-25 that just experienced a speed limit increase in April, this portion of I-225 was improved through the T-REX project, making it necessary to increase the speed limit to improve safety," said CDOT Traffic Engineer
Steve Hersey. "The existing speed limit was appropriate for travel on a roadway with lower design standards than the reconstructed highway we see today."
CDOT's engineering studies utilize nationally-accepted methods which take into account roadside features, roadway geometric characteristics, accident history, and vehicle speeds. The national standard recommends use of the 85th percentile speed (the speed at or below which 85 percent of the vehicles are moving) as the primary factor in establishing the speed limit. The reason for this is because the vast majority of drivers will drive at speeds they consider safe and reasonable under ideal conditions.
The study I-225 found 85th percentile speeds around 70 mph in the study segment. CDOT's goal is to set the appropriate speed limit so that the maximum number of vehicles travel at about the same speed, thus reducing conflicts caused by extreme speed differentials.