Experts: No ‘magic bullet’ for Perimeter traffic snarls

The Sandy Springs mayor wants Pill Hill shuttle services running from new MARTA parking garages. Some residents want to widen Hammond Drive; some want to keep suburban-style streets. The rapidly growing city is building multiuse trails and talking about monorails.

There’s no shortage of ideas for fixing the Perimeter Center area’s increasingly tangled traffic, but there are plenty of questions about which ones will work. Local experts say there are no easy answers and many different alternatives will be needed. The downside: traffic is getting harder to predict, and the impact of some commuting solutions is difficult to measure.

“There’s no silver bullet here, no magic bullet,” said Michael Hunter, a traffic engineering professor at Georgia Tech. “It really should be a multi-alternative approach, especially when you’re looking at a complicated area like this.”

“Rarely can you ever actually solve [traffic congestion],” Hunter said, describing more of a problem-management approach. “Usually, it does end up being a collection of different [solutions]…Putting in a shuttle may make sense in one area and make absolutely no sense in another area.”

Jennifer Harper at Perimeter Connects knows a lot about those shuttles, and carpools, and discount MARTA passes. Harper helps employers use those solutions and more in the alternative commuting program administered by the Perimeter Community Improvement Districts. She agrees that the challenge is targeting the alternatives to the proper situations.

“Telecommuting’s not going to work for everyone. MARTA’s not going to work for everyone,” Harper said. Instead, Perimeter Connects works on a “personalized plan for each company.”

When experts like these look at how to tailor such solutions in a place like Sandy Springs, they start with “capacity” and “demand.” Capacity is what engineers like Hunter mostly handle: physical infrastructure like roads and traffic signals. Demand is what alternative transportation consultants like Harper mostly handle: methods for reducing the number of single-occupant cars on the road.

“Capacity and demand are the two big things,” said Hunter, emphasizing the need to “look at both parts of the equation.”

And of course, the lines between them aren’t strict. Hunter noted that, without careful design, new road projects can trigger “induced demand”—attracting more traffic—as well as “latent demand,” where drivers who avoided a nasty road return when it improves, causing it to quickly clog up once more.

What engineers see
Traffic engineers like to start by studying the heck out of the situation, Hunter said.

“The first thing you need to do is, you need to figure out what’s going on,” which may not be what average drivers expect or assume.

A curveball in traffic studies, Hunter said, are commuting apps like Waze and Uber-type private taxi services. Such technology makes traffic more unpredictable, and while some people believe technology like driverless cars could solve everything, they’re full of potential for “unintended consequences,” he said.

“Is there anything innovative I can do?” Hunter said is a question engineers ask. One such innovation is the “diverging diamond” interchange that speeds up intersection flow by allowing traffic to swap sides of the street. A diverging diamond is already installed on Ashford-Dunwoody Road at I-285 in Dunwoody, and another is coming to Sandy Springs’ Abernathy Road at Ga. 400.

Capacity is also about trade-offs, Hunter said, noting it’s possible to build a giant road to handle rush-hour traffic that is empty concrete the rest of the time. “Where do you want to live? How do you want the area to look?” he asked, saying residents might answer, “I can live with more congestion a few hours a day if it means we get fewer lanes, more green space, more bike lanes.”

That’s not a pure engineering choice, but a “societal choice, a political choice,” Hunter said. “Make it an active choice instead of something that just happens as we go along.”

What commuting experts see
At Perimeter Connects, Harper deals with the dramatically different needs of hospitals, Perimeter Mall and Fortune 500 companies.

“We’re a very unique market. We’re a bit different than Buckhead or Midtown or Downtown,” she said. “You market to each of them very differently.”

Some of that work is behind-the-scenes detail, like helping Pill Hill hospitals adjust their shift schedules to better match MARTA. Some is helping coordinate major public efforts like the three new Georgia Regional Transportation Authority bus routes coming to Perimeter Center, with the first debuting in September.

Perimeter Connects helps coordinate one Perimeter Center shuttle service; about a dozen corporations have their own as well. And it supervises staggered-shift programs by major corporations so they don’t all simply move rush hour to another time.

Commuting is a concern for the PCIDs itself, which has a new office in Sandy Springs. Harper said some employees take MARTA—the office is near North Springs station—while some others “moved specifically here in the market so they’re not commuting.” But Harper herself lives in Brookhaven and has kids in different camp programs, meaning it’s car travel for Perimeter Connects’ program manager.

That mix of alternatives is common in the quest to “reduce single-occupancy trips as much as we possibly can,” as Harper put it.

But which programs are actually working? The data is limited. Perimeter Connects knows how many discount MARTA passes sell and that the local shuttle is full. But the best option—people working from home—is “nearly impossible” to measure. In fact, telecommuting programs often fizzle because companies lack the “nuts and bolts, hardware and software” to make it practical—services that Perimeter Connects is stepping up consulting efforts to improve, Harper said.