Expressway incidents are a major problem resulting in loss of lives and property in metropolitan regions across the world. At the same time, traffic incidents are one of the important causes of traffic congestion. Vehicles in traffic incidents are often difficult to evacuate from the scene in time due to various reasons, and it is also difficult to move to the side of the road without affecting the normal traffic flow, resulting in incident vehicles occupying one or more lanes, which greatly reduces road traffic capacity. Traffic jams caused by traffic incidents on the expressway are particularly noticeable. Even minor traffic incidents often require a lot of time to complete traffic control. As a result, the road where the incident occurred will be in a state of low capacity for a long time, and the congestion will spread to the road network along the line and the surrounding road network in a certain order. Especially during rush hour, the normal road traffic capacity can no longer meet the smooth driving of vehicles, and the traffic capacity caused by incidents further decreases, which makes the current road congestion intensify and affects other parts of the road network. 

Project Motivation

Traffic incident have a negative impact on social life in terms of traffic congestion. The most immediate impact is increased travel time and costs for residents. The increase in travel costs not only affects work efficiency, but also inhibits people's daily activities, and the quality of life of residents also decreases. However, in traffic planning, the negative impact of traffic congestion caused by traffic incident is very difficult to quantify. As technology advances, devices such as traffic cameras, on-board sensors, and GPS are widely used to collect data on traffic conditions, traffic jams, and vehicle speeds. These data provide new opportunities for us to further explore the relationship between traffic incidents and traffic congestion. This study develops a data-driven approach to explore the impact of incidents (Dec, 2014 – Dec, 2015) on the highway system. 

Research Questions

• How long will the traffic congestion caused by expressway incidents last?

• How much will expressway incidents reduce the road speeds?

• How far would the expressway incidents cause traffic congestion?

Methodology 

This project mainly uses the method of classifying expressway incidents to calculate their impact on traffic congestion. I divided the incidents into four categories by road type and incident injury degree: Freeway Fatal Incident, Tollway Fatal Incident, Freeway Type A Injured Incident, and Tollway Type A Injured Incident. Then I used the method of calculating average duration and average speed to calculate each The average congestion duration and average speed reduction caused by a classified incident. Then, I used spatial statistics to calculate the impact distance of traffic congestion by adding up the lengths of the road sections affected by the congestion in the incident up and down stream.

Summary 

This study provides a method to verify real time probe incident data and explores the impact of expressway incidents on traffic congestion, include duration, speed reduction, impact distance. Impact analysis reveals fatal and serious injury incidents will reduce 50% faster average travel speed, average duration of decelerations associated with fatal incidents 3.5 hours and with  serious injury incidents1 hour. Affected mileage varies large, but the collision will cause the speed to be reduced 9 miles long.