Smart traffic signals assist the blind in crossing the street

Credit: Anna Boyle/ Credit: Anna Boyle/

For most of us, crossing the street is as routine and simple as eating and drinking. But for people who are visually impaired or who have other disabilities that impede their ability to move freely, crossing the street can be a stressful experience at best in a traffic system not always designed with their needs in mind.

Researchers at Carnegie Mellon’s Robotics Institute, with the help of a $2 million grant from the Federal Highway Administration (FHWA), are aiming to change this situation by researching smart traffic signals that can communicate directly with smartphones and adjust green-light times to accommodate those with disabilities who would require longer times to cross an intersection, or warn the user if the traffic signal detects that he or she is moving outside the intersection.

One of the project’s leaders, Stephen Smith, a professor of robotics, revealed the thought process behind the idea of using smart traffic signals to better accommodate those with special needs in an interview with The Tartan.

“I began thinking about the idea a few years ago after giving a talk on our traffic signal control work to the Golden Triangle Council for the Blind, and hearing their perspectives and problems on pedestrian navigation through intersections,” recalled Smith.

Thus, when he heard about the Accessible Transportation Technology Research Initiative (ATTRI) sponsored by FHWA, he seized the opportunity to start exploring the idea of using technology to mitigate the issues that special-needs pedestrians face at intersections.

“My group had already been working in the area integrating adaptive signal control with emerging “connected vehicle” technology, where vehicles equipped with dedicated short range communication (DSRC) radios communicate directly with the intersection, and extending direct communication to pedestrians with disabilities seemed like a natural idea,” explained Smith.

Smith and the team involved in the project aim to develop a mobile app that can run on a smartphone equipped with DSRC capability, which will facilitate the main part of the communication between pedestrian and intersection traffic signals. They also hope to integrate this communication feature with Surtrac, a system combining artificial intelligence, traffic theory, and real-time traffic data to optimize traffic signal control to reduce waiting times, congestion, and pollution. Surtract was also developed in Carnegie Mellon’s Robotics Institute and led by Smith with support from the school’s Traffic21 and Metro21 initiatives. Surtrac already has shown tangible benefits: according to a university press release, in Pittsburgh, Surtrac has “reduce[d] travel time by 25 percent, braking by 30 percent, and idling by more than 40 percent.”

“Most basically, the app will encode and allow communication of the pedestrian’s personal crossing constraints (namely travel speed) to the intersection, and the signal control system will ensure that the pedestrian is given sufficient green time to cross,” Smith explains.

Additionally, the app will also make use of the smartphone’s GPS system to monitor whether the pedestrian is crossing outside of the crosswalk and whether it is necessary to further adjust the traffic signal timing based on the pedestrian’s progress through the intersection. The team also plans to use route information from the pedestrian’s smartphone to streamline their travel by anticipating the user’s arrival at certain intersections.

Smith says the team plans to do field testing with volunteers from the local blind community in the East End of Pittsburgh, where the Surtrac system has already been deployed, and eventually develop a system that can work for people who have other disabilities as well. It could be useful to many people who live in suburban areas where pedestrians are infrequent and signals do not always accommodate them.

Since smartphones do not generally have built-in DSRC capabilities, the testing will require outfitting a DSRC sleeve to the testing subjects’ smartphones, but future phone models could integrate such a feature if it proves useful, according to Smith in a university press release. Ultimately, the driving force behind the project is integrating modern technology into our infrastructure in order to improve safety and mobility for pedestrians with disabilities.