In Tokyo, Joshy Kasahara didn’t have to drive a car.
When he came to Collegedale to attend Southern Adventist University, Kasahara had to adjust to the highway traffic in the Chattanooga area.
“It should be easy to drive,” the graduate student said in an interview. “The space is so limited in Tokyo. We don’t have many lanes. The speed is a lot slower.”
When it came time to do a project with real-world applications for a data visualization course, Kasahara chose to tackle local traffic.
The interactive map Kasahara created puts historical data about crashes on area highways into an interactive interface. Users can zoom in on their local on-ramp or see where they’re most prone to wreck, or use the heat map feature to see general trends.
“Data science is actionable,” professor Harvey Alférez said in an interview. “These results have to be shared. In this case, we do believe that we have the responsibility to share these results to the general population of Chattanooga so they can be more aware of the issues in traffic — especially in some particular red areas you can see.”
To no one’s surprise, the area around the split at Interstates 75 and 24 is a hotspot for crashes, the map shows.
(READ MORE: East Ridge Police Department identifies victims in I-75 crash)
“People have to do the lane changes,” Kasahara said of that junction.
The map also shows a higher volume of crashes around the ridge cut on I-24, the interchange with Highway 27 near downtown Chattanooga and along Highway 153 in Hixson.
“There’s many people moving into Chattanooga from out-of-state,” Kasahara said, noting they don’t immediately know their way around. “California, Colorado, you name it.
“I designed this to be interesting enough for people to interact,” he continued. “There was no data visualization that was understandable for ordinary people on where accidents are happening.”
You can access the map online at bit.ly/ChattDrive.
THE DATA
The map represents data from almost 1,600 crashes between November 2020 through April 2021.
In the future, Kasahara said he’d like to expand it to include real-time information, or at least more up-to-date numbers.
“People pointed out it’s nice to have live data,” he said. “I see it’s feasible to bring the live data to this data dashboard. That’s future work.”
But finding reliable, clean data to put into a map like this is hard, he said.
(READ MORE: Chattanooga drivers urged to seek interstate alternatives)
The dataset he used was already cleaned, used in a paper published by the Tennessee Department of Transportation and the Oak Ridge National Laboratory. Researchers did a lot of work to make the data usable, Kasahara said.
“So, for instance, they cleaned up the weather data,” he said. “Sometimes, some police officers input the weather or time of the accident or location inaccurate, so the researchers did correct some.”
Arrows on the map show users which direction a driver was going before a wreck. Users can toggle settings to focus on different factors, like accidents with injuries, involving pedestrians or collisions with things like guardrails or light poles.
Kasahara zoomed in on the map, toggling some buttons to show accidents, including “deer (animal).”
A few yellow arrows showed up near Enterprise South Nature Park. But then — an arrow rounding the I-24 curve before downtown Chattanooga.
“In downtown!” Kasahara said. “So, hey, be careful. That’s a kind of uniqueness to Chattanooga. This doesn’t happen in Tokyo, ever.”
Residents and visitors can play around with the map and make surprising discoveries like this one, Alférez said.
There are also larger trends that come out as users toggle the settings.
Daylight plays a large role in accidents, data shows — around 55% of crashes happened in the dark.
Just three accidents on the highways involved pedestrians, the map shows, and all of them took place in the dark. Two were hit-and-runs.
About 15% of the incidents on the map were hit-and-runs, the data shows.
“Coming from Tokyo, Japan, it’s a little bit high,” Kasahara said.
Fourteen of those incidents resulted in one or more deaths, according to the data.
Kasahara said working on the map has made him feel more knowledgeable about the area and connected to the community.
“I feel like I have become more like a local,” he said.
Contact Ellen Gerst at egerst@timesfreepress.com or 423-757-6319.
Staff photo by Ellen Gerst / On June 5, 2025, Southern Adventist University graduate student Joshy Kasahara and professor Harvey Alférez present Kasahara’s data visualization project, a map showing where accidents happen on Chattanooga area highways, at the university’s Hickman Science Center.