To those in the traffic engineering profession, it has become quite evident that traffic has substantially decreased (in most places) as a result of all the policies and orders put into place to first encourage, and now mandate “social distancing”. These decreases are not, however, uniform, nor are they predictable. Some efforts have been made to quantify the effects; however, given the short time frame the data sets we have do not have sufficient inputs to determine statistical validity. Whether we have already reached a new mean, or if we instead will be experiencing peaks and valleys correlated to individual needs/wants/desires as they relate to interpretations of the ever-changing government mandates has yet to be seen.
What We Are Seeing on the Roadways
The NCDOT Transportation Planning Division has been reporting a significant drop in overall traffic week by week for the month of March 2020.
Estimated Change in Travel
The numbers shown in the chart also do not reflect the “stay at home” order signed by NC’s Governor that went into effect on March 30 th , but it would be expected to see even more substantial drops. It will take a little more time yet to see how much greater that impact may be statewide, but surrogate measures can be evaluated now, drawing from counties where these orders went into effect earlier.
Buncombe County was early to shut down all but essential businesses, and some preliminary numbers show significant drops. Looking first at the number of crashes reported, the Asheville Police Department filed 243 crash reports between March 16-26 in 2019. For that same time period in 2020, there were only 95, representing a 61% drop in crashes. The drop in daily traffic volumes during the month of March is quite evident. The NCDOT Mountain Traffic Management Center reported the following for Hendersonville Road (US 25):
As a result of these substantial decreases in ADT, it is quite likely that vehicles that normally would be waiting for traffic to clear to turn (permitted left and right turns) will have far shorter wait times. It also means that signals where a protected movement has been necessary to create gaps in traffic are now creating substantial delays for turning and crossing movements where there is no longer any conflicting traffic. These shifting patterns are likely far different than before, to the extent that it may be worth adjusting signal timings. Since we are looking at another several weeks before the Governor’s order expires, and probably many months before traffic stabilizes to a new normal after that, consideration should be given to adjust signal operations.