Four to three
Four lanes become three.
Projected: about 29% fewer crashes where it’s built
Anyone who drives Montgomery Avenue knows the move. The car ahead stops to turn left, and you either hit the brakes or swing into the other lane and hope nobody’s there. The study flags this weaving and sudden braking as a key problem, and more than half of the corridor’s reportable crashes are angle crashes, the kind turning traffic tends to cause.
The fix is mostly paint: one through lane each way, with a turn lane in the middle. Turning cars get out of the way, through traffic stops weaving, and people on foot have fewer lanes to cross. Federal studies found 19% to 47% fewer crashes after conversions like this. The study’s 29% is the Federal Highway Administration’s combined estimate. For suburban roads like this one, FHWA suggests planning on 19%, which would still be a big drop.
This has been done nearby. In 2022–23, PennDOT converted nearly a mile of Wynnewood Road in Lower Merion the same way, with a design that included bike lanes, paid for with federal money. It isn’t a new idea for Montgomery Avenue either. At a 2018 Penn Valley Civic Association meeting about the stretch near Narberth, residents brought up a three-lane plan from 2005, and a civic leader suggested trying a pilot.
Full conversions are proposed in parts of Rosemont and Narberth; one-direction conversions in parts of Bryn Mawr, Merion and Bala Cynwyd. Sources: FHWA Road Diet Informational Guide (2014, archived). FHWA listed road diets as a “proven safety countermeasure” from 2012 until July 2026, when it removed them without publicly explaining why (the list before the change; NPR).