Odd Route 309 intersection raises question on left turns

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— Ed Schulz, Upper Saucon Township


A: My first-gear sense was that opposing left-turning vehicles should pass each other before turning left at this unusual, challenging intersection, Ed, and I'm happy to report that PennDOT traffic engineers agreed.


This intersection features an unusual (though not unique) layout. Two-lane Camp Meeting Road (to the east) and Lanark Road (west) meet the separated four-lane highway of Route 309 at a signalized intersection just before 309's convergence to the north.

A sort of half-way zone lies in the area between the parted highway lanes, with the end of the grass median to the south and the start of the concrete median barrier to the north. In the course of turning left onto 309, motorists on each of the side streets cross this midsection, which is a bit longer than at the average intersection.

PennDOT engineer Tom Walter said in an email that he's seen motorists use both methods in making the turns — turning in front of one another, passenger-side to passenger-side, or proceeding straight, passing driver-side to driver-side, and subsequently making the turn. So it can work either way, though as you say, Ed, it's important that both drivers take the same approach to avoid bending fenders.

"Based on the configuration of the intersection [wide spread between northbound and southbound lanes], and to make the turning maneuver safely, I would say the left-turn maneuvers should be made behind each other," Walter wrote. "There is ample room for left-turning vehicles to pass one another and then make their turn."

This somehow seems safer than passing in front of each other, though I'm not sure why. Vehicles pass in front of each other fairly frequently at "regular" signalized intersections where two opposing left-turners enter the intersection to wait for lane traffic to clear; if both cars are able to turn at the same time (normally because the light begins its change sequence), they go ahead and do so, quite safely. Still, this maneuver seems a little tricky, and I try to make sure I keep my distance from the other car. It's as though a minor sideswipe on the passenger sides might be more likely than on the driver sides, simply because it would occur on the sides of the car farther from the drivers. Or maybe I'm just imagining things.

After observing the patterns at 309 and Camp Meeting, I realized that opposing through traffic forces left turners to wait initially (if they're observing the rules, anyway), which would tend to make the "passing behind" option the intuitive response.

In the photo, the van in the center and the white pickup truck behind it are completing the passing-behind turn; the van had to wait for the two vehicles to clear the intersection anyway, so it made sense for that driver to allow the pickup to pass as well. During my 45-minute observation, all the simultaneous left turns were taken this way. That's not to say the turn-first approach doesn't happen, but I suspect it's in the minority.

So the layout here is a little odd, and in a perfect world, the intersection would be moved slightly north, to a point where the opposing highway lanes are adjacent, allowing for a familiar, square signalized intersection.

However, I've seen a variation of the same kind of "safe zone" concept used intentionally, and effectively, on Route 1 in Middlesex Township, Delaware, where we vacationed in August. Also known as the Coastal Highway in that area, Route 1 is a separated four-lane highway maybe not as busy as 309 in Center Valley, but heavily traveled in vacation season, and, being an American road, is subject to many drivers going a little too fast most of the time.

The design is used even at non-signalized intersections controlled by stop signs. The safe-harbor area between the lanes, a bit wider than at 309, allows motorists to cross the first pair of lanes when traffic from the left is clear, then wait in the safe zone for a break in traffic from the right. This allows cars to get through the intersection by avoiding the need for a break in highway traffic from both directions at once.

The safe zones even feature lane lines and turning arrows to help guide motorists through the movements — an important addition, as left-turners from the zone must avoid blocking traffic from the right that's turning left into the zone; that traffic passes in front.

The design seemed confusing at first, but I quickly came to admire it for its efficiency, so long as everyone plays nice and observes the rules.

At the end of the road, you probably wouldn't be cited for making your left turns either way at 309 and Camp Meeting, Ed — unless you happened to get into a fender-bender, in which case an officer might decide to cite someone.

If it were I wearing the badge, I'd write up the other guy. Unfortunately, I'm not a cop, so you're on your own.


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