The Impact of Road Design and Infrastructure on Car Accident Rates

In recent years, there has been a growing recognition of the crucial role that road design and infrastructure plays in the incidence of car accidents. The objective of road design and infrastructure is to provide a safe and efficient transportation system, reducing the number and severity of crashes, and improving mobility for all users. However, that doesn’t always happen. Some roads and highways are known for being dangerous.

Highway on-ramps, stretches of highway, intersections – any of these can become dangerous. For example, data from the Texas DOT show that some of the most dangerous intersections in Houston are:

• Pease Street and Fannin Street
• Bissonnet Street and Westchester Avenue
• Main Street and Montrose Boulevard (Mecom Fountain Roundabout)
• FM 1960 and W. Lake Houston Parkway
• S. Gessner Road and Westpark Drive
• Spencer Road and Highway 6
• Highway 6 and Bellaire Boulevard
• Treaschwig Road and FM 1960
• Clay Road and Barker Cypress Road
• Highway 6 and Westheimer Road

In Dallas, some highways are known for being dangerous, according to data from the Texas DOT include:

• LBJ Freeway from I-35E to Dallas North Tollway 
• Central Expressway from LBJ Freeway to I-30
•  I-45 from I-30 to Lamar
• LBJ Freeway from Dallas North Tollway to Central Expressway
• Woodall Rodgers Freeway from Stemmons to Central Expressway

Until self driving cars eliminate motor vehicle accidents, dangerous road design is something that impacts us all in Texas.

Factors Influencing Car Accident Rates in Road Design

 Several factors play a role in the impact of road design on car accident rates. These include:

• Lane width and shoulder width: Narrow lanes and inadequate shoulder width increase the risk of sideswipe and run-off-road crashes.
• Curve design: Poorly designed curves increase the risk of head-on and run-off-road crashes.
• Grade and alignment: Poor grade and alignment can lead to run-off-road crashes, especially in adverse weather conditions.
• Intersection design: Poorly designed intersections can increase the risk of angle and turning crashes.
• Lighting: Insufficient lighting at intersections, along highways and on bridges can contribute to crashes.
• Road signs and markings: Inadequate or confusing road signs and markings can contribute to crashes, especially in rural areas.

Mitigating the Impact of Road Design on Car Accident Rates

To mitigate the impact of road design on car accident rates, transportation engineers and planners use a variety of strategies and techniques. These include:

• Implementing proven safety countermeasures: For example, installing median barriers and rumble strips to reduce the risk of run-off-road crashes.
• Improving road design: For example, designing roads with wider lanes, better curves and safer intersections.
• Conducting safety audits: Conducting regular safety audits of roads can identify potential safety problems and lead to targeted improvements.
• Incorporating technology: Using technology such as Intelligent Transportation Systems (ITS) and Advanced Traffic Management Systems (ATMS) to improve safety and mobility.
• Engaging stakeholders: Collaborating with stakeholders, including local communities and road user groups, can help ensure that safety is integrated into road design and infrastructure decisions.

Glossary of Terms

Lane width: The width of a lane on a roadway, expressed in feet or meters.

Shoulder width: The width of the shoulder of a roadway, expressed in feet or meters.

Curve design: The design of a curve in a roadway, including the radius and superelevation.

 Grade and alignment: The slope and horizontal alignment of a roadway, expressed in percent grade and horizontal curvature.

Intersection design: The design of intersections, including the placement of stop signs, traffic signals, and crosswalks.

Lighting: Illumination of a roadway, including streetlights and overhead lighting.

Road signs and markings: Signs and markings used to provide guidance and information to road users, including warning signs, regulatory signs, and pavement markings.

Median barrier: A physical barrier separating opposing lanes of traffic on a divided highway.

Rumble strips: Raised pavement markers used to alert drivers of potential hazards.

Intelligent Transportation Systems (ITS): A range of technologies used to improve safety, efficiency, and mobility in the transportation system.

Advanced Traffic Management Systems (ATMS): Technologies used to manage traffic flow and reduce congestion, including traffic signals, ramp meters, and dynamic message signs.