In July and August 2014, the Pennsylvania Department of Transportation (PennDOT) and Pennsylvania Turnpike Commission (PTC) raised the posted speed limit on rural sections of Interstates 80, 380, and 76 from 65 to 70 miles per hour (mph). This was considered phase one of a broader initiative. The following locations were included in the posted speed limit increase: • Interstate 80 Eastbound (EB) near Dubois Interchange Exit 101: Segment 1010, Offset 2090 to Interstate 80 EB near State Route (SR) 477 Interchange Exit 185: Segment 1860, Offset 369. • Interstate 80 Westbound (WB) near Dubois Interchange Exit 101: Segment 1001, Offset 2433 to Interstate 80 WB near SR 477 Interchange Exit 185: Segment 1845, Offset 1057. • Interstate 380 Southbound (SB) near the Interstate 84 Interchange: Segment 0231, Offset 0045 to Interstate 380 SB near Exit 8: Segment 0095, Offset 1500. • Interstate 380 Northbound (NB) near Tobyhanna Exit 8: Segment 0094, Offset 1600 to Interstate 380 near the Interstate 84 Interchange: Segment 0230, Offset 0045. • Interstate 76 EB near Blue Mountain Interchange Exit 201: Milepost 200.90 to Interstate 76 EB near Morgantown Interchange Exit 298: Milepost 299.74. • Interstate 76 WB near Blue Mountain Interchange Exit 201: Milepost 200.90 to Interstate 76 WB near Morgantown Interchange Exit 298: Milepost 297.40. In order for PennDOT and the PTC to determine if additional segments of rural Interstate highway should be considered for the 70 mph posted speed, an assessment of the speed and safety performance of the “pilot” sections is needed. The purpose of this project was to compare operating speeds and crash frequencies before and after the posted speed limit was increased. Additionally, operating speed data in several work zones were collected to assess how drivers comply with posted speed limits in work zones, and to evaluate how driver speed choice changes from non-work zone to work zone locations. Additionally, an inferred design speed method and pavement friction degradation method are proposed as methodologies to assess site conditions on rural Interstate roadways with 65 mph posted speed limits. Collectively, the operating speed, safety, inferred design speed, and friction information can be used by PennDOT and the PTC to identify candidate locations for 70 mph posted speed limits. This report is organized into nine subsequent sections. The first provides background information about posted speed limits in the United States. A general discussion about the relationship between speed and safety is described in the second section of the report. The third section of the report is a literature review of extant literature related to the speed and safety effects of changing posted speed limits. An overview of the objective analyses performed in the present study is provided in the fourth section of the report. The fifth section describes the operating speed evaluations performed at both non-work zone and work zone locations on PennDOT and PTC-operated rural Interstates. The sixth section describes the safety assessment of these same roadways. An inferred design speed evaluation for the PTC is provided in the seventh section, and the eighth section describes the pavement friction assessment. The final section of the report offers conclusions from the evaluation. (Author/publisher)
Samenvatting