Skewed Intersections

Example of skewed intersections, image displays skewed intersection in an urban area


Intersections are vital components of road networks, serving as critical points where traffic flows intersect and diverge. However, intersections also account for a large portion of road-safety problems in the United States. Per the National Highway Traffic Safety Administration (NHTSA), approximately 22 percent of fatal collisions and more than 40 percent of total traffic collisions occur at or are related to intersections. In particular, skewed intersections, characterized by their non-perpendicular alignment of roads, present unique challenges that can significantly compromise road safety. 

Limited Visibility

One of the most apparent dangers associated with skewed intersections is limited visibility. When roads converge at non-perpendicular angles, the ability to provide adequate sight distance triangles within the built environment can be impacted. This reduced sight distance can lead to shorter distances where opposing operators are able to see one another, making it challenging for them to make safe decisions.

Confusing Traffic Patterns

Severely skewed intersections can cause confusion among all roadway users, including drivers, pedestrians, and cyclists. The irregular alignment of roads can make it difficult for road users to interpret the right-of-way rules, leading to hesitation and potential conflicts between vehicles. This confusion can be exacerbated when traffic signals are not appropriately placed or when signage is unclear due to the skewed roadways making the signage visible for multiple, conflicting approaches. Such uncertainty can increase the likelihood of incidents and disrupt the flow of traffic.

Increased Turning Difficulty

Negotiating turns at skewed intersections can be more challenging than at standard perpendicular intersections. Drivers making turns may struggle to gauge the turning radius accurately, leading to wide or abrupt turns that pose a danger to other road users. This difficulty is particularly concerning for large vehicles like trucks and buses, which may require more space to maneuver, potentially encroaching into other lanes or obstructing traffic.

Higher Speed Differentials

Skewed intersections can lead to higher speed differentials between intersecting roads. Vehicles coming from different directions might have varying speeds, especially on multi-lane roads.  As a result, drivers trying to merge into the flow of traffic may find it challenging to match the speed of other vehicles after taking sharp turns at the lower speeds necessary for their smaller turn radius. This speed discrepancy increases the risk of rear-end collisions and side-impact crashes when drivers fail to adjust their speed adequately.

Limited Safe Crossing Opportunities

For pedestrians and cyclists, skewed intersections can present substantial safety concerns. Crossing roads at non-perpendicular angles might not provide clearly defined pedestrian crossings or bike lanes. This lack of dedicated crossing opportunities forces vulnerable road users to navigate through irregularly shaped spaces, increasing their exposure to vehicles and compromising their safety. Furthermore, skewed intersections result in longer crossing distances for pedestrians and facilitate higher speed turning movements by vehicles along the larger radius turns associated with the intersection.

Challenging Design and Implementation of Traffic Control Measures

Applying effective traffic control measures at skewed intersections can be complex. The standard traffic signal configurations for perpendicular intersections might not be directly applicable or optimally effective for skewed ones. Design engineers may need to devise specialized traffic signal timing, lane designations, and signage to accommodate the unique geometry of these intersections. 

Categories: Civil Engineering | Premise Liability

Tags: Intersection | NHTSA | Traffic Control | Transportation Safety


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