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Top Highway Safety Expert Says Lane Expansion “Will Increase Both the Number and Severity of Crashes on US-75.”

The following information was provided to Sioux Center Citizens for Responsible Growth by Tom Welch, an internationally recognized safety expert who was the head safety engineer of the Iowa DOT and the project manager on the nationally acclaimed “road diet” for Sioux Center, when Sioux Center reduced Main Street from 4 lanes to 3, reducing crashes by 57% and eliminating personal injuries and fatalities completely!

Mr. Welch’s project received national awards because of its safety results. An expert on Highway 75, our group asked him to review all of the traffic data for Sioux Center and tell us what the data says about whether an expansion is safe. Here is what he said:

Earlier this year on behalf of Mark Perington [Principal Traffic Engineer at Snyder & Associates, Inc. and consultant to the City of Sioux Center and the Iowa DOT] I sent an e-mail to over 250 Highway Safety professionals around the country in every state asking if they were aware of any 3 lane roadways being widened to 5 lanes? NOBODY was aware of such a widening project. So there is no past study of the safety impact of widening a 3 lane road to a 5 lane roadway.

During my career as a Safety Engineer I reviewed the best research available relative to the Safety Impact of converting a 4 lane UNdivided roadway to either:

  1. A 4-lane DIVIDED roadway (concrete island in center of the roadway)
  2. A 5-lane roadway
  3. A 3-lane roadway

The 4-lane DIVIDED roadway improved safety the most, the 3-lane roadway was the second best way to improve the safety of a 4-lane UNdivided roadway and the conversion to a 5-lane improved the safety the least.

This shows that 3-lanes are inherently safer than 5-lanes.

My findings were later substantiated by a later study by the Minnesota Dept. of Transportation (MNDOT). The MNDOT calculated the accident rate on various URBAN street designs. Again the 4-lane DIVIDED streets had the lowest accident rate and the 3-lane streets had a substantially lower accident rate than 5 lane streets.

I can not envision any scenario that would result in the accident rate on US-75 in Sioux Center being lower after the road is widened to 5 lanes. A 5-lane roadway will NOT be safer than the current 3-lane roadway.

  • There will be more conflict points where the paths of vehicles could cause a collision(i.e. a left turning vehicle off of US-75 now only crosses the path of one approaching vehicle, with a 5-lane roadway it will need to cross the path of 2 approaching vehicles.
  • Average travel speeds will increase and more importantly, the percentage of vehicles driving more than 5 mph above the speed limit (aggressive drivers) will increase very significantly. See Iowa DOT before after study on the US-75 4-lane to 3-lane conversion.
  • The increased speeds will not only contribute to more crashes , the severity of those crashes will be greater – more serious injury crashes and possibly more fatal crashes.
  • Younger drivers are always over represented at intersection crashes . The reason is not because they are poorer drivers. Rather that part of the brain — which allows them to pass judgment on how far away an approaching vehicle is and how fast that approaching vehicle going — is not fully developed until a person is in their early 20′s.
  • Older drivers are also over represented at intersection crashes. Again, that same part of the brain which is not fully developed in teenagers is often the first part of the brain of an older person deteriorate.

As such, younger and older drivers will often pull out in front not only other cars but semi-trucks, causing a broad side crash. Broad side crashes result in the most severe crashes, often fatal to older drivers in particular.

There are other reasons why a 5-lane roadway will increase both the number and severity of crashes on US-75, but the above the above discussion should suffice even for most skeptical person.

You have my permission to share my above engineering judgement with any one you choose.

Tom Welch, P.E.

welchAbout Mr. Welch: He retired as the Iowa DOT Safety Engineer in 2010.  He was the project  manager  for the 4 lane to 3 lane conversion on US-75 . Tom has been involved in numerous studies on 4-lane to 3-lane conversions and is considered a national expert on the topic. He is currently  developing a 4-lane to 3-lane conversion guidance document for the Federal Highway Administration.In 2004 Tom was awarded the American Association of State Highway and Transportation Officials Presidents Award of Merit for his “outstanding leadership,innovation and dedication to safety initiatives across America.” He is the only State Safety engineer to have ever received this award.In 2011 the National Academies of Science send Tom to China after China requested a Safety Engineer come to Beijing to visit  with their Safety Engineers.