Innovative Low Cost Strategies
Case study data shows the effectiveness of the low-cost approach in creating safe driving conditions for motorists.
The Pennsylvania DOT has designed and implemented several innovative strategies to treat safety problems. Many of these approaches reflect a low cost approach to traffic engineering. As presented in Table 6, these strategies are generally designed to improve safety through improved signing and pavement marking programs.
| Treatment | Description | Cost | Effectiveness |
|---|---|---|---|
| Advance curve warning | Developed to help motorists reduce speed when approaching curve. The pavement marking consists of two transverse bars, a "SLOW" legend, and an arrow indicating the direction of the upcoming curve. |
Approximately $1,350 per site | Based on the evaluation of the original pilot program, there is expected to be a reduction of the 90th percentile speed. This translates into an estimated 25% reduction in curve-related deaths at each of the locations where installation is planned. |
| "Dot" tailgating treatment | Idea is to reduce tailgating by installing "dot" shaped pavement markings at fixed intervals such that keeping two markings apart will provide a safe following distance. | Approximately $1,800 per site | Police in South Centre Township observed a significant drop in tailgating and speeding in the area of the dots. |
| Intersection warning treatment | Concept is to provide advance warning to drivers proceeding through intersections under "Stop" - sign control. A series of signs and pavement markings assist drivers in judging gaps between on-coming vehicles. | Approximately $5,000 per intersection | Experimental program under evaluation. |
Pennsylvania DOT's Advanced Curve Warning Treatment
The advanced curve warning treatment warns drivers to reduce speeds.
The advanced curve warning treatment is a pavement marking placed on the roadway indicating that the driver should reduce speed for an upcoming curve. This treatment is being promoted in sections of roads or corridors with higher than average numbers of crashes having roadway curvature as a contributing factor. The pavement marking consists of two transverse bars, a "SLOW" legend and an arrow indicating the direction of the upcoming curve.
The overall objective is to reduce the upper percentile speed, thus reducing the number of vehicles leaving the roadway and being involved in a crash. The total estimated cost per site, including pavement markings, installation labor, and equipment was approximately $1,350. Based on the evaluation of the original pilot program, there is expected to be a reduction of the 90th percentile speed. This translates into an estimated 25% reduction in curve-related deaths at each location where installation is planned. The larger pilot involves the treatment of nearly 200 sites with the advanced curve warning treatment.
Pennsylvania DOT's "Dot" Tailgating Treatment
Dot treatment signage indicates safe following distances.
The "dot" tailgating treatment marking is an effective highway safety countermeasure for assisting motorists in establishing safe following distances. This treatment is being promoted in sections of roads or corridors with higher than average numbers of crashes linked to aggressive driving or tailgating and where traffic congestion is not anticipated. Markings are spaced such that a minimum of two markings separates vehicles, which allows for a safe distance between them. Initially the Department tried painted chevrons on the pavement, with the spacing between chevrons based on the 2-second rule; however, the public had some difficulty in understanding what the chevrons meant. To address tailgating crash problems and motorists' confusion with chevrons, the Department decided to identify the area with signing and dot pavement markings, educate the motoring public with press releases and media events, and have targeted additional enforcement at particular problem areas in the corridor.
Figure 1. Pennsylvania DOT Intersection Warning Treatment. Roadway markings help guide drivers where roadways intersect at grade.
The total cost per installation is approximately $1,892 including signs, labor, and equipment. A test site was deployed in South Center Township since rear-end crashes represented 43% of the crashes on the US 11 corridor. South Centre Township police reported that they have observed a significant drop in tailgating and speeding in the area of the dots, and in the area north of the dots there has been a 60% drop in crashes based on a comparison of the following time periods:
- 11/1/99 to 3/1/00 = 34 crashes
- 11/1/00 to 3/1/01 = 12 crashes
The appendix to this primer contains the Guidelines for Installation of Pennsylvania "Dot" Tailgating Treatment and Design Specifications.
Pennsylvania DOT Intersection Warning Treatment
This treatment is used on a pilot basis when data show a high occurrence of crashes where vehicles on secondary roadways intersecting at grade misjudge the gap between approaching vehicles. Markings are placed to indicate safe gap length for a vehicle to accelerate from a stop into the intersection. Safe distance is defined based on posted speed for the primary roadway. The entire treatment consists of the following components: 1) placement of legend "SLOW, xxMPH" and 2) "+" symbols on the primary roadway, and 3) placement of appropriate signs on the secondary roadway.
