Bus bulbs are going in at several RapidRide stops along the new C and D lines.

A bus bulb extends the sidewalk at a bus stop out into the parking lane of the street. The bus simply stops in the travel lane instead of pulling out of traffic and back in again after serving the stop. This makes bus service faster.

Yes, vehicles behind the bus have to wait while the bus pauses to pick up and/or drop off passengers. But traffic studies by the City of Seattle show minimal delays to traffic flow from bus bulbs. In Ballard along the D Line, morning peak-period congestion is expected to remain mostly unchanged at all 10 intersections between NW 85th Street and Leary Avenue NW since the morning peak-hour travel lane was converted to bus bulbs and parking.

Photo: bus and cars at bus stop in front of Fauntleroy Ferry Terminal.
Cars wait behind a bus serving a new bus bulb at the northbound stop in front of the Fauntleroy Ferry Terminal.

Travel time is expected to be a bit longer for general-purpose vehicles, with a southbound increase of about 50 seconds during the morning peak between NW 85th Street and NW Market Street.

But travel times for buses are expected to improve by 1.5 to 2 minutes, depending on the time of day, along the same section of road. This benefit comes partly from the bus bulbs, and also partly from other transit priority improvements that have been made as part of the RapidRide program, including transit signal priority at each intersection with a traffic signal.

Bus bulbs have additional benefits, including increased parking and wider lanes for general-purpose travel. D Line bus bulbs on 15th Avenue NW between NW 80th Street and NW 67th Street will bring back 24-hour on-street parking, for an estimated net increase of 105 parking spaces in morning peak hours.

The outside travel lane will also be widened slightly, providing more room for the larger freight vehicles that use the corridor. In Ballard, D Line bus bulbs will create a southbound two-lane roadway at all hours, like the street profile on 15th Avenue NW between NW 65th Street and NW Market Street.

And stops with bus bulbs have more space for passenger amenities — like shelters, benches, and real-time bus arrival signs — and their added waiting space helps keep sidewalks clear for pedestrians.

NOTE: This post was updated on 9/13 to reflect that the City of Seattle’s traffic studies were completed before bus bulbs were installed, so they measured expected rather than actual effects on traffic flow.