While there has been an emphasis on improving safety along corridors, it is equally important to focus on identifying potential safety issues at intersections.
A GS&P-designed intersection in Tennessee
As non-vehicular modes of transportation become increasingly popular, cities are working to address the safety needs of all modes of transportation, including vehicles, bikers and pedestrians. While there has been an emphasis on improving safety along corridors, it is equally important to focus on identifying potential safety issues at intersections. Intersections are a point in our roadway system where various traffic movements and modes of transportation directly conflict with one another. Signalized intersections naturally create a risk, but unsignalized intersections can pose a more serious driving hazard.
Under our District 7 Access Management Safety Studies contract with the Florida Department of Transportation (FDOT), Gresham, Smith and Partners has been working to address high crash locations within the District, which covers five counties in the Tampa Bay area. Specifically, we were tasked with evaluating 100 unsignalized intersections that had the highest crash severity index, which is determined by the number of fatal and serious injury crashes, and identifying short-term, mid-term and long-term solutions to identify and address future roadway improvement projects.
Based on initial discussions with FDOT’s District 7 and Central Office staff, we learned that the state’s top safety issues included rural lane departure crashes, intersection crashes, distracted drivers, wrong way drivers, and pedestrian and bicycle safety. To begin addressing FDOT’s concerns, we employed the strategies outlined in the 2016 Florida Strategic Highway Safety Plan, a set of guidelines created to reduce fatalities and injuries on Florida’s roadways, as well as provide multimodal accommodations. The plan shifts the focus from corridors to intersections, evaluating safety conditions as they relate to all users. To reduce the frequency and severity of crashes at intersections and reduce conflict risks, the plan suggests reviewing operations and safety for all intersection users, as well as evaluating crash data hot spots.
As we analyzed the high crash locations, our team worked to identify potential safety issues and remedial actions. In addition, the Federal Highway Administration’s Crash Modification Factors (CMF) Clearinghouse allowed us to use lifecycle cost and net present value formulas to do a benefit-cost analysis in determining viable improvements.
The FHWA’s Crash Modification Factors Clearinghouse uses lifecycle cost and net present value formulas to do a benefit-cost analysis, which helps determine future projects.
As an example, when applied to the intersection of SR 45 (US 41) and Carson Drive in Pasco County, Florida, the CMF Clearinghouse analysis recommended the following short-term improvements:
- Install a high-visibility crosswalk across Carson Drive;
- Close the westbound median opening;
- Extend the southbound left-turn lanes;
- Install additional signage; and
- Install stop bars at the driveways in proximity to the intersection.
Proposed improvements for SR 45 (US 41) at Carson Drive to create a safer unsignalized intersection.
After analyzing FDOT’s 100 high crash locations and using the FHWA’s Crash Modification Factors Clearinghouse, I drew two conclusions about addressing roadway safety at unsignalized intersections. First, I believe the focus on safety should shift from corridors to intersections, as the higher-risk locations need continuous safety monitoring. Second, I think that while long-term improvement projects may be inevitable at some locations, a number of short-term and mid-term improvements can take care of many roadway deficiencies. For improvements to be efficient, however, on-going processes should build off of previous improvements.
As transportation engineers and planners, it’s important that we encourage safe environments that support motorized and non-motorized modes of transportation. The number of pedestrians and bikers is growing, making intersection safety even more important. By working to identify high crash locations and developing both short-term and long-term improvement plans to address these areas, we can create communities that support all modes of transportation.