Why Transit Should be in the Fast Lane
Local buses tend to use the slow lane, which in North America means the rightmost lane; this is how they access the curb to pick up passengers. New York’s painted bus lanes on First and Second Avenues are to the right, with the buses slower than the cars both in perception and in actual practice.
Occasionally, transit uses the fast lane, especially if it’s BRT or a streetcar; for some of the access challenges of boarding not from the curb, see an old Human Transit thread on the subject. The issue of whether there should be sidewalk- or median-adjacent transit lanes came up in comments on Cap’n Transit’s blog. So let me explain why higher-grade transit than local buses, which means rail or BRT, should run in the median, with boarding from raised curbs either on the sides or in the center.
1. Service identity. This is probably the overarching concern, especially on the question of whether to have raised curbs or instead stop traffic in the slow lanes and have people cross to the bus from the sidewalk. ITDP’s magnum opus standards for full-fat BRT virtually take median running for granted, and only consider alternatives when the right-of-way is constrained. This is also mentioned as the highest grade of BRT in a conference paper examining BRT on city streets.
2. Fewer conflicts. Using pedestrian-friendly two-phase stoplights, it is impossible to eliminate turn conflicts, though in Delhi they found that median running (right lane in India) had fewer turn conflicts. In addition, it’s possible to eliminate conflicts with cars entering or exiting the parking lanes, as well as stopped cars left near the curbside lanes.
3. Median lanes are politically easier to physically separate, since separating them does not deprive cars of curbside access. If cars can physically violate transit lanes, they will, either accidentally or intentionally (my mother’s car’s GPS guidance routinely sends her along the tram-only lanes). As APTA mentions in its own standards for BRT,
One major advantage of a median busway is that there is typically no demand for other vehicles to stop in the center of the street for purposes such as parking or as a breakdown lane. As a result, there is a lot less reason for vehicles to want to occupy the center of the road and less resistance to creating a physical barrier separation between the busway and the adjacent general traffic lanes.
Point #3 is what killed the proposal for the 34th Street Transitway, which would have run two-way on one side of the street with one direction running contraflow. The NIMBYs on East 34th Street complained specifically about curbside access, using such language as “Delivery and service trucks… no longer have direct access to buildings and stores along stretches of 34th Street.” Most issues they raised involved curbside access or else bus noise adjacent to the street, both of which would have been solved by median lanes.
To add to what Steve Stofka is writing about grids, if I had to design a street from scratch, it would look a lot like a two-way version of a Manhattan avenue, with bus lanes in the middle. It would be 30 meters building to building, and about 20 curb to curb; this is enough space for two parking/loading lanes (2.5 meters) buffering pedestrians from moving traffic, two car travel lanes (3 meters), and two median bus lanes (3-3.5 meters), with room left for physical separation (measured in centimeters). Raised curbs for stations should add 3-4 meters, at the expense of either parking or sidewalk space once every few hundred meters; one advantage of trams, or buses with doors on both sides, is that they can use less space-consuming island stations.
Pedestrian Observations 
Where are the bicyclists in your hypothetical street redesign? And how will left turns off the street be made?
Cycle lanes could be between the sidewalk and the parked cars. They probably wouldn’t be full-fat Dutch-standard lanes (2.5 meters one-way), but they’d be good enough for Copenhagen (1.5-2 meters). It would marginally narrow the sidewalks to about 4.5 meters.
Left-turns would be made the same way they’re made on two-way streets today. Those transit lanes are not going to be Transmilenio systems with headways measured in seconds – at first-world wages, it’s cheaper to first run trams every few minutes and subsequently build rapid transit – which means that most of the time, there’s not going to be any turn conflict. A bus driving at 30 km/h across a 30-meter street blocks turning cars for 3.6 seconds; schedule two of these in succession and it’s still 7.2 seconds out of about 40 that the light is green.
two median bus lanes (3-3.5 meters) – btw, streetcars are 2.3-2.6m wide. The right of way doesn’t have to be much wider.
I’m working on how bike lanes can be in the median as well. We have a lot of streets that are built for high volume rush hour traffic that are empty during the regular workday. I think giving priority and permission(meaning stricter enforcement of bike accidents that are the fault of cars) to bikes and buses in the center turn lane in the midday might help people see the options, then consider a rush hour change of traffic volume.
“with the buses slower than the cars both in perception and in actual practice.”
By definition, buses and streetcars will always be slower than cars. They have to stop every so often for passengers, private cars do not.
As for left turns, cities like San Francisco and Sao Paulo, even without transit lanes, simply ban the practice to improve traffic flow. Three rights make a left.
A bus with its own lane will be faster than a car on a congested street.
Detroit is still wondering weather to do center or curbside (like the private-3 million each-investors want). That’s on a 550 million dollar system (that goes to 8 Mile)-not beyond.
I’ll be passing this one on.