[image-1]The results are in for a study examining the potential effects of closing a lane of traffic across the Ashley River to add a pedestrian/bike lane.

If you’ll remember, between April 2 and May 13, one northbound lane of the Legare Bridge was closed off to figure out just what might happen if a dedicated bike lane was put into place to provide commuters a safe path when crossing between West Ashley and downtown Charleston by bike. For the first few weeks, traffic heading north on Folly Road was required to merge from two lanes into a single lane just past the intersection of Folly and Albemarle Road. We’ll call this Test 1. For the final two weeks of the study, the location of this required merge was moved up closer to the bridge to measure the difference in travel times. As you’ve probably guessed, this is referred to as Test 2. So let’s take a look at the results.

Traffic on Folly Road from Maybank Highway to Lockwood Drive was the most affected by the lane closure. The study reports an increased average delay of one minute 47 seconds between 7 a.m.-9 a.m. for Test 1. Average delays during the peak 30 minutes within this morning period rose by four minutes 47 seconds. Test 1 had less of an effect on those traveling U.S. 17 and S.C. 61. In what the report calls a “moderate increase,” travel times on U.S. 17 from Wesley Drive to Lockwood Drive increased by about 22 seconds during the morning hours. S.C. 61 was the least affected by the test, with drivers experiencing an increase of only six seconds.

Test 2, which the report says provided drivers on Folly Road with a longer distance to merge, showed improved conditions for morning commute times on Folly Road. Average travel time increase during the peak 30 minutes dropped from four minutes 47 seconds found during Test 1 to just over one minute. The overall average delay for the two-hour morning period was 48 seconds. The same could not be said for drivers on U.S. 17 and S.C. 61. During the two-hour window, the lane shift being moved closer to the bridge resulted in a 40 second delay on U.S. 17 and a 14 second delay on S.C. 61.

According to the recent report, a traffic simulation conducted in 2015 to predict the effects of a lane closure on the bridge “understated the changes in travel times that would be anticipated” — primarily as it concerns Folly Road. One difference pointed out between the real-world test and the simulation was that actual drivers “appeared to be less aggressive when congestion occurred in the merge area” compared to their computer counterparts.