International Cooperation to Prevent Collisions at Intersections

Public Roads, July, 2001 by Cathy Frye

The United States and Japan have joined forces in the hope of finding technology-based solutions to reduce the high incidence of crashes at intersections. Teaming together for the new U.S.-Japan Intelligent Transportation Systems (ITS) Joint Research Program, both countries are exchanging information and discussing solutions being developed, evaluated, or implemented in their respective nations.

The ITS Joint Research Program was initiated in November 2000 in Turin, Italy, during the 8th Workshop on ITS in the United States and Japan. The workshop was held in conjunction with the 7th World Congress on Intelligent Transport. The workshop participants laid the groundwork for the future cooperative study and agreed that their long-range research topic will be the evaluation of the effects of infrastructure support for intersection collision avoidance (ICA). In addition to exchanging progress reports throughout the year, Joint Research Program participants will hold an annual meeting to review findings.

Each year, both countries will focus on one research subtopic for study The topic for 2001 is systems concepts and requirements for infrastructure support for ICA.

In the spirit of "two heads are better than one," both countries will take this opportunity to look at solutions that are aimed at reducing the number of crashes at intersections in the United States and Japan. Because the two countries frequently take different approaches to resolve the same problem -- too many accidents occurring at intersections -- the Joint Research Program is a learning experience for all involved.

To further advance the Joint Research Program's information exchange, Japan is sending an engineer to the Turner-Fairbank Highway Research Center each year on a fellowship. Having a Japanese research fellow at the Federal Highway Administration's (FHWA's) center for research, development, and technology helps in the day-to-day informal exchanges of information. Both countries are excited about the potential advances in intersection collision avoidance that could come from this cooperation.

At the Cross Roads or in the Cross Hairs?

According to the International Road Traffic Accident Database, an estimated 10 million traffic crashes worldwide occur each year, and these crashes claim the lives of one-half million people. Sixty percent of the crashes occur in the United States, and of those, 27 percent of the crashes in the United States occur at intersections. Intersection crashes are in a statistical dead heat with rear-end collisions, which account for 28 percent of all crashes on U.S. roads, as the second most common type of crash occurring on our roads. This makes intersections "among the most dangerous locations on U.S. roads," according to FHWA's ITS Joint Program Office.

In Japan, intersection collision statistics are even more staggering; more than 58 percent of all traffic crashes occur at intersections. Thirty percent of all Japanese traffic accidents involving fatalities occur at intersections, and the majority of these fatal crashes happen at intersections without traffic signals.

Intersections Present Unique Problems

The crash statistics from both the United States and Japan clearly show the dangerous nature of intersections. Intersections are far more complicated than other roadways, such as a divided highway where all of the traffic on each side of a median is flowing in one direction. Since an intersection is a decision point for vehicles from multiple directions, many variables are at play. Vehicles may need to stop, start, yield right of way, slow, accelerate, or turn. Drivers may purposefully ignore traffic signals -- as is often the case with red-light running -- or simply misunderstand them.

Intersections present the ideal environment for crossing-path crashes in which both vehicles are initially traveling from either perpendicular or opposite directions and then one vehicle cuts across the path of the other. There are four types of crossing-path crashes:

* Straight crossing paths (SCP).

* Right/left turn into path (R/LTIP).

* Left turn across path -- lateral direction conflict (LTAP/LD).

* Left turn across path -- opposite direction (LTAP/OD).

In addition to vehicular crashes, pedestrian accidents in intersections are also a problem. In the United States, 70,000 vehicle-pedestrian collisions occur annually, and 40 percent occur in intersections. More than 45 percent of all pedestrians hit by vehicles in Japan are struck in an intersection, and an astonishing 52 percent of these incidents occur while the pedestrian is in the crosswalk.

The Weak Link

Surprisingly, the cause of most crashes is not adverse road conditions, driving under the influence, or even vehicle defects. In the human-machine collaboration that occurs during driving, the weak link is often the human. Driver error is the cause of 90 percent of all police-reported car crashes in the United States.

Preliminary study data from the ITS Joint Program Office indicate that with the full deployment of just three Intelligent Vehicle Initiative (IVI) systems, one in every six U.S. crashes would not occur. IVI systems are being designed to enhance human performance and guard against human shortfalls such as limited sight distance and reaction times that are not fast enough to keep a crash from happening.