Regular users of the Northeast Corridor in New Jersey know that there is a short branch off the line serving Princeton. Mainline trains do not use it – they continue between New York and Trenton – but a two-car shuttle, affectionately called the Dinky, connects the city with the train station. Historically, this is because the Northeast Corridor in New Jersey is a then-high-speed rail cutoff from 1863, which cut off Princeton from the old line. Trains run back and forth, with timed connections between New York (but not Trenton) and Princeton.
The Princeton stop on the Dinky, as can be seen in the satellite image, lies just outside the historic municipal limits of Princeton (since merged with the surrounding township). It serves the university fairly well, but is 800 meters at closest approach to the town’s main street, Nassau Street. So there has been a study for what to do to improve city access, in which a tram-train option was studied, looked good, and was dropped anyway. There are two options left: status quo, and a downgrade of the right-of-way to light rail with buses using the same corridor.
Unfortunately, transit advocates I respect, like Sandy Johnston, think the downgrade is an upgrade. So let me explain why in fact the light rail and bus option is inferior to current commuter rail operations.
The current use of the Dinky is as a connector to the Northeast Corridor. There is approximately nothing else at Princeton Junction: it’s one of the two busiest suburban stations in New Jersey, but like the other top station, Metropark, it’s a park-and-ride, designed exclusively for car-train interface. People who ride the Dinky do so to get to New York.
This means that the timed transfer with the mainline trains is critical. Frequency on the Dinky is irrelevant: all ridership from Princeton Junction into the town is going to be on the first train or bus after the mainline trains arrive, and almost all ridership to the junction is going to be on the last train that makes the connection. While frequency is not important except insofar as it matches that of the mainline, on-train capacity is important. My 2015 recollection is that off-peak ridership on the Dinky is maybe enough to fill an articulated bus (which New Jersey Transit only runs in Newark), maybe enough for a standard bus, depending on time of day – standees are likely, and standing on a bus is an awful passenger experience. At rush hour, the Dinky
runs three-car trains (update 2022-2-18: no, it’s two-car trains) and they’re full.
The timed transfer is so important that the discussion of how to improve service must center how to make the transfer more efficient. The ideal improvement should be to regularize the timetable on the mainline commuter trains, and ensure that trains in opposite directions serve Princeton Junction around the same time (this is called a knot) so that the Dinky can connect to Trenton too, and even to Philadelphia with another timed transfer at Trenton or even through-service if that fits the New Jersey Transit and SEPTA schedules.
Sandy points out to me that while the Dinky only connects Princeton with the mainline, the right-of-way of the Dinky can serve more destinations – namely, the Route 1 job cluster, visible on the map as a line of office parks.
However, bus service from town to Route 1 is unlikely to succeed. It’s going to struggle to run sufficient frequency for what it needs, even as lower-frequency rail is sufficient for the Dinky’s current role:
- Route 1 is not on the way between town and the station – there would have to be separate buses to Route 1 from the service to the train station (which I presume will stay on rail even if the downgrade is picked). This means there’s no bundling of destinations – the buses to Route 1 have to live off of Princeton-Route 1 trips.
- Route 1 is a freeway with destinations located somewhat away, at automobile scale. Buses can stop on the side of the road but the walk is not great on the same side of the road and hostile and unsafe if crossing the road is required. A more pleasant experience is only possible if buses turn onto side roads, splitting frequency or increasing trip times.
- Route 1 is not a large job center. OnTheMap says that between the route of the Dinky and the junction with I-295 beyond the above satellite image, which ends at Quakerbridge Road, there are 21,000 jobs. The origins of those jobs are dispersed – only 5,000 come from within the county, and only 368 come from within Princeton.
- Conversely, the short distance traveled means that high frequency is crucial. A one-way trip from the townhouses just north of Nassau Street to the center of the Route 1 cluster along the right-of-way of the Dinky is 5.5 km, which at BRT and freeway speed is around 10 minutes one-way; a bus running less than once every 10 minutes might as well not run – but there is no chance for such a bus to fill at current demand.
Of course, the analysis of Route 1 assumes current development patterns stay with no or moderate change. A bigger change, such as greater development along Route 1 with sprawl repair, can make this option pencil out; O&D volumes need to rise by a factor of 3 assuming 100% transit modal split, or more if modal split is lower (which it invariably is, Route 1 is not Manhattan).
But then that raises the question – why engage in development in sprawl around a plan to downgrade a rail service?
If sprawl repair is plausible, then make Princeton more bikable and then set up bike lanes on Route 1 so that people can cycle to Route 1 jobs. The same bike lanes can also connect to the Dinky, with bike parking at the station, or even potentially at Princeton Junction if it’s faster to bike those 4 km than to ride a train and transfer. In the long run, all buses are going to have to be replaced by bikes anyway – bus operating costs are only going to go up.
And if redevelopment is plausible, look again at the satellite image and see what the land use at the existing train stations is like. Princeton is one of the most expensive places in the United States, and the Dinky station has a golf course on one side; that’s 0.5 km^2 of land, or, as I prefer to think of it, 50,000 housing units. Another 0.05 km^2 consists of parking lots right near the station, and can and should be redeveloped as a town center extension for a population that can swamp the existing town population by a factor of 4. The parking lots at Princeton Junction and the undeveloped land between them are another 0.4 km^2 of prime real estate.
In general, I cannot think of any railway where service would be improved by a downgrade from mainline rail to bus. But the Dinky has specific issues making such a downgrade especially deleterious for current users, namely the need for a timed connection, while the proposed source of new trips, namely Route 1, is too weak to be worth much. Thankfully, a no-build option keeping the status quo is still under consideration, and I hope that the region chooses it and invests in making the Dinky better rather than in replacing it.