SAN ANTONIO – Traffic jams are ever increasing in San Antonio and are known to get a commuter's blood boiling. Many of the causes behind all those brake lights are well know, including losses of lanes, wrecks and rubbernecking.
"There's a crash in the opposite direction and everybody on my side of the road feels like they need to be an amateur insurance investigator," said traffic engineer for the Texas Transportation Institute, Tim Lomax.
However, there are some aspects of traffic jams that are more complicated and, in some cases, still being investigated. Lomax, who has studied traffic for most of his professional career, explained that phenomena like the not-so-technical "slinky effect" are ideas that commuter often do not understand. It begins when a driver gets too close to the person in front of them and lightly taps the brakes.
"Three cars behind tap their brakes, three cars behind them have to slam on their brakes, or hit their brakes a little bit harder, and that causes what we essentially call a ‘slinky effect,'" said Lomax.
In essence, a wreck can happen well ahead of where a commuter might be, but all of that braking gets passed backwards, sometimes several miles.
"People are now going very slowly a mile or two upstream," said Lomax. "By the time they get to where the crash used to be, things are flowing fine."
Other times, all it takes is one slow truck in the right lane. Drivers in adjacent lanes do not feel comfortable passing at higher speeds, so a ‘slow-down' is passed across the highway from right to left. Holidays can also play a part in slow commutes. According to Lomax, some of the busier days for evening commutes occur on Halloween and Valentine's Day, because everyone is attempting to get home at the same time.
Statistics also show that today's drivers are far more brave because of added safety features and are more comfortable with less space between cars. This results in more vehicles on a freeway at once.
"From the mid 60s until now, the theoretically capacity of our freeways have gone from 1,800 to 2,400 cars per lane per hour," said Lomax.
Researchers, like Lomax, are working on solutions to traffic jam issues; one of those solutions being slower speed limits. The idea is currently being tried on certain stretches of Loop 1604 with variable speed limits. The theory is that more people driving at an average speed versus variable speeds will reduce the 'slinky effect' and ironically cut down on commute times.
Meanwhile, San Antonio is expected to see commute times increase as the city's growth continues.