How the speed limit policy affects travel speed?: Quasi-experimental approach

Abstract

Abstract The objective of this study is to examine the effect of posted speed limit change on travel speeds. To do this, we use the National Performance Management Research Data Set (NPMRDS), which is a unique and rich dataset provided via the Federal Highway Administration (FHWA). Particularly, we focus on the impact of increased posted speed limit, implemented during June 2015, on interstate highways in Wisconsin including urban and rural areas between 2014 and 2016 by employing a quasi-experimental model with a panel dataset. Our findings clearly demonstrate that the posted speed limit change from 65 to 70 increases travel speed by 1.7 mph after controlling for location and time specific fixed-effects. Specifically, the posted speed limit change on Wisconsin interstate highways increases average travel speed of passenger and freight vehicles by 1.87 and 1.16 mph, respectively. Findings also show that speed variations have increased after the speed limit change, and higher variations do not occur in freight travel speeds, but in passenger vehicle travel speeds. These variations differently exist between urban and rural areas. We suggest that transportation agencies should consider these variations by vehicle types and places when they increase posted speed limit.