I81 Traffic
Traffic is bumper to bumper traveling Southbound on Interstate 81 at the Lingelstown exit in Lower Paxton Twp. Thursday August 19, 2010. CHRIS KNIGHT, The Patriot-News
(CHRIS KNIGHT, The Patriot-News, 2010)
A simple rule governs transportation planning in Pennsylvania: Not enough money is available to fix every road, bridge or on-ramp in need of repair, so the worst are at the top of the list, and those that can make-do, make-do.
Among the factors planners use to determine which road or bridge receives priority status is, naturally enough, driving conditions.
For years, transportation planners have relied on car counts — literally paying someone to count cars — to figure out what was happening on area roads.
But what if they could get into commuters' cars? What if planners could measure what's actually happening on the area's highways and intersections and not just rely on estimates drawn from a single snapshot in time?
This summer, when the Tri-County Regional Planning Commission released its annual traffic congestion report, it did exactly that.
At her desk in Harrisburg, planner Jamie Lemon taps a few keys and on the screen, a map of the midstate starts to populate with yellow and red dots.
Using data collected anonymously from GPS units, transportation planners can generate maps like this one, which show congestion on area roads.
Each one is a congestion point, based on hundreds if not thousands of measurements by anonymous drivers. The data are collected through the GPS units sitting on commuters' and truckers' dashboards. The companies that sell those GPS units — and provide the satellite service — collect anonymous user data on an aggregate level.
Want to know what the average speed is along Interstate 83 during rush hour? According to Tri-County, it's 34 mph, roughly half of what speeds typically are on the highway. I-83 typically ties up traffic all the way from Interstate 81 to south of the York split.
At it's peak, it would take a driver six times as long to travel I-83 than it would under normal conditions — far and away the worst road in the region. Which is also one of the reasons why it will be the subject of a more than $20 million state Transportation Department project later this summer.
Access to detailed information at this level can help planners prioritize traffic projects or identify roads and intersections that are causing queuing during peak travel times.
This data also can change commonly held beliefs. When the agency released its congestion report earlier this year, it included roads that everyone knows are bad, specifically the I-83 York split. But I-81 wasn't included because, according to the data, congestion on I-81 has decreased over the past several years.
It was, Lemon said, a bit of a surprise.
The next two most worst roads in terms of peak travel delay also may surprise some: Sporting Hill Road in Hampden Township and Route 39 in Susquehanna Township.
Other roads on the list included:
- Routes 11/15 in Camp Hill,
- Mountain Road in Lower Paxton Township,
- Carlisle Pike,
- Route 114 in Upper Allen Township.