Ask ELi: What Is a “Road Diet” and Does It Make EL Safer?

Wednesday, June 6, 2018, 7:41 am
By: 
Thomas Baumann

Photo above: A section of Harrison Road after it was given a “road diet.”

Another section of Harrison Road is due to be put on a “road diet” soon. So what is a road diet, which roads in East Lansing have been put on one, what is the evidence they have made East Lansing roads safer?

How road diets create safer conditions:

The process of either narrowing or eliminating travel lanes for vehicles to make a roadway safer by reducing speed, providing a center turn lane, and adding dedicated space for cyclists, is often called a “road diet.” But it really should be called a “safety conversion,” since the main objective is to create a safer roadway for drivers, cyclists, and pedestrians. Traffic space is not removed but reassigned to create a safer roadway and to accommodate bicyclists.

A road diet often involves dividing up the space of a four-lane road into two lanes, a center turn lane, and two bike lanes (as shown above). Sometimes additional space for pedestrians or on-street parking is provided.

By adding a center turn lane, left-turning vehicles no longer hold up traffic that is going straight, and cars that are going straight don’t have to make a lane change to get around a left-turning vehicle that is waiting for traffic to clear. Road diets also calm traffic because, with only one through-traffic lane going each way, weaving through traffic from lane to lane is no longer allowed.

At intersections, with a road diet, there are fewer conflict points, and so crossing or entering the road becomes safer. It’s also safer for pedestrians at crosswalks, because they are crossing two lanes of traffic instead of four lanes. The bike lanes also add a buffer between pedestrians on the sidewalk and car traffic.

For many four-lane roads, these safety conversions result in a significant safety improvement with no or minimal negative effect on traffic flow. Studies have shown that, using this kind of approach, the overall crash rate is reduced by 19% to 47%.

Which roads in East Lansing have seen a “road diet” and what has been the result in terms of safety, car congestion, and drivers cutting through neighborhoods?

East Lansing has a long history of employing road diets, and a very successful one. Burcham Drive (shown below) was converted from four lanes to three lanes in 1996, Grand River Avenue west of Michigan Avenue was converted in 1997, and Abbot Road was converted from Burcham Drive to Saginaw Street in 1999.

These three conversions were analyzed in a 2001 study by Michigan State University’s Department of Civil and Environmental Engineering. An overall crash reduction was observed, with the largest improvement for pedestrians and bicyclists.

The same study also simulated traffic flow for the Abbot Road conversion in more detail. It found that, up to a traffic volume of 2,000 vehicles per hour, there is very little effect on the average delay on the main road. Since the traffic volume on these roadways is well below this number (a recent traffic impact study for Abbot Road shows a maximum traffic volume of about 1,000 vehicles during the p.m. peak hour), the road conversion should have very little effect on travel time.

Because of this, there should also be no additional incentive for drivers to cut through the neighborhood.

How are decisions made in East Lansing about which roads to put on a “road diet”?

Road diets are implemented after input from adjoining neighborhoods, City of East Lansing staff, East Lansing’s Transportation Commission, and the general public. To help in the decision making, traffic impact studies might be ordered, and sometimes public hearings are held. For road segments that fall under a different jurisdiction (like Grand River Avenue, which is a State owned and State-operated road), the process can be much more complicated.

In general, road improvements involve expenditures and thus, in East Lansing, must be approved by City Council. That does not mean every technical detail is scrutinized by Council, but details are reviewed by City engineers and often discussed with the Transportation Commission.

Even if City Council approves a road conversion, that does not mean it is implemented right away. Chris Wolf, who served on the Transportation Commission from 1998 to 2006, notes that, in order to save money, all of the road conversions in East Lansing have been performed as part of a scheduled repaving, not as a standalone project. The result is that some conversions approved by City Council took a long time before they were done.

For example, the three-lane conversion of Harrison Road between Saginaw Street and Lake Lansing Road was approved by City Council in 2002, but was only executed in 2016. A conversion of Coolidge Road (four lanes plus bike lanes) was also approved by Council in 2002, but with the condition that the conversion will only happen at the time of the road is repaved. This has not happened yet.

Not all road conversions are approved. Take the case of Hagadorn Road between Grand River Avenue and Haslett Road, which came before Council in 2006 but was not approved.

If these are such a great idea, why do they always seem to stir up controversy?

Road conversions are a great idea if your primary goal is safety, but they are certainly not a fix-it-all. Depending on traffic volume and other considerations, they might not be the best solution for a particular road.

Studies show that road segments with an average traffic volume of 10,000 or fewer vehicles per day are good candidates. If the traffic volume is too high, the result could be increased delays and congestion.

But there are other factors to take in account besides traffic volume: How much side street traffic entering the roadway has to be accommodated? Does the altered roadway provide enough stacking space at signalized intersections? If the delays become too big, or the road becomes congested, drivers might use alternate routes. In some cases that can be acceptable, in other cases not. So, a detailed traffic study is necessary.

Chris Wolf contributed reporting to this article.

 

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