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Navigation tools may be directing drivers to shortest but more dangerous routes

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Comparing routes between five metropolitan areas, Texas A&M University researchers found that navigation systems were often guiding drivers to follow paths that carried a greater risk of crashes.

Comparing the safest and shortest routes between five metropolitan areas in Texas – Dallas-Fort Worth, Waco, Austin, Houston and Bryan-College Station – including more than 29,000 road segments, the research team from Texas A&M found that taking a route with an 8 per cent reduction in travel time could increase the risk of being in a crash by 23 per cent.

Researchers Dominique Lord and Soheil Sohrabi designed a study to examine the safety of navigational tools. They collected and combined road and traffic characteristics, including geometry design, number of lanes, lane width, lighting, average daily traffic, weather conditions, and historical crash data, to analyse and develop statistical models for predicting the risk of being involved in crashes.

The study revealed inconsistencies in the shortest and safest routes. In clear weather conditions, taking the shortest route instead of the safest between Dallas-Fort Worth and Bryan-College Station will reduce the travel time by 8 per cent. However, the probability of a crash increases to 20 per cent. The analysis suggests that taking the longest route between Austin and Houston with an 11 per cent increase in travel time results in a 1 per cent decrease in the daily probability of crashes.

Overall, local roads with a higher risk of crashes include poor geometric designs, drainage problems, lack of lighting and a higher risk of wildlife-vehicle collisions.

“As route guidance systems aim to find the shortest path between a beginning and ending point, they can misguide drivers to take routes that may minimise travel time, but concurrently, carry a greater risk of crashes,” said Lord, professor in the Zachry Department of Civil and Environmental Engineering.

The researchers propose a new system architecture to find the safest route using navigation systems.

“Our study revealed the potential of commonly used road navigation apps to misguide users toward using a road that carries a higher risk of crashes, which implies the need for considering safety in route-finding,” Sohrabi said. “Developing such a system is, however, challenging. We proposed a system architecture for safe route-finding and highlighted the requirements for and barriers in incorporating safety in navigation apps.”

In the new system architecture for finding the safest route, the researchers said that after receiving the trip destination and time of day, the algorithm would identify routes by using the road network data and possible incidents, including road or lane closures due to flooding or crashes. The system would also factor in road characteristics, historical crash data, traffic information and current weather conditions. The route with the lowest accumulated risk would then be suggested as the safest route.

“Navigation based on safety, rather than travel time, can result in preventing crashes and promoting overall safety on the road network and eventually save lives,” Lord said.

While this proposed system is promising, it is heavily dependent on the availability of data by local and federal government agencies responsible for road transportation. The requirements for deploying safety in route-finding systems also include the availability of real-time traffic flow and incident reports and more accurate crash prediction models.

Additionally, including a safety consideration in navigation apps would introduce the issue of a trade-off between travel time and safety. Researchers said drivers who aren’t concerned with safety might take a route with a higher risk of crashes to reduce travel time, but all road users are affected if a collision occurs.

“Given the fact that crashes can affect not only those involved but also other road users, leaving the choice between safety and time to the users may result in unethical decisions and unfair consequences,” Sohrabi said.

Additional work is needed, they said, to address some of the limitations in the study, such as distinguishing directional crash risk, intersection crash risks and the severity of crashes along these routes.

The study – 'Navigating to safety: Necessity, requirements, and barriers to considering safety in route finding' – has been published in the transportation journal Transportation Research Part C.

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