Amid the massive overhaul of the 23rd Ave corridor and the uproar it’s caused with local merchants, another project on the street has quietly got underway: building the infrastructure necessary to transition the route 48 diesel hybrid busses into a fleet of all-electric trolleys.

Connecting the U-District to Mt. Baker through the Central District and Capitol Hill, the 48 is the workhorse of 23rd Ave transit, shuttling riders the entire length of the corridor. Much of 23rd Ave has overhead wires to accommodate the 4 and 43, but the 48 has to run diesel hybrid busses due to gaps in the line.

There are currently 1.7 miles of missing overhead wires needed to run electric trolleys on the 48, with gaps from John to Cherry, and Dearborn to Plum.

The Seattle Department of Transportation, which is handling funding and construction for the King County Metro line, estimates the project will cost $14.6 – $17.5 million, with $9.4 million already secured through federal grants. Construction will include installing trolley poles, overhead wires, and traction power sub stations. The second phase of the project is expected to get underway next year, setting up the 48 to go electric in 2018.

“The Electric trolley bus is the really tried and true transit wet have here in Seattle,” said SDOT’s transit deputy director Bill Bryant at a recent city-county joint transportation meeting. “It is particularly well suited for our hilly environment and lots of starts and stops.”

There are clear environmental benefits, too. With its 4 miles per gallon busses, the 48 route uses roughy 185,000 gallons of diesel fuel a year. Electric trolley bus technology was found to be $3.7 million cheaper annually than diesel hybrids, according to an SDOT study. Electric trolleys will also significantly reduce noise along the busy corridor.

In 2023, the 48 will also be the only transit line to directly connect non-downtown stations on all three Link lines: Central Link (Mount Baker Station), East Link (Judkins Park Station), and North Link (Brooklyn and UW stations).

Transit riders are increasingly using electric modes of transportation around Capitol Hill and the Central District. The First Hill Streetcar and Capitol Hill light rail station carry thousands of riders a day on zero-emission trains. Metro is also making further investments in its electric trolley bus fleet, and has started a limited roll out of battery-powered busses.

Electrifying the 48 is happening as a massive road construction project on 23rd Ave spanning Montlake, Capitol Hill, and the Central District seeks to transform the street into a new configuration with a center left-turn lane while improving the pedestrian and sidewalk experience. The new layout will allow buses to pull completely out of the traffic lane at stops. Crews are also replacing a 100-year-old water main between E Madison and E Union.

As SDOT changed its phasing schedule to keep the project on track late last year, some 23rd Ave merchants said business had dwindled to a trickle as the street overhaul has diverted traffic and pushed pedestrians off sidewalks. After saying his administration had no legal recourse to help, Mayor Ed Murray relented and announced a $650,000 fund had been established to help mitigate the impacts of construction. The first $25,000 checks for businesses were cut this month.