Monday, 11 April 2011

Baltimore's "Quickbus", and the tradeoffs made for fast buses (part 1)

Baltimore, like most cities of under a million people, is a city whose public transport is nearly all composed from local buses; with the exceptions of from a small metro line and a single light rail line. Given its ambitious plans for rail expansion, it's clearly quite ashamed of this.

And frankly, it probably should be ashamed of its bus system. As well as often being operated by old, high-floor buses, services are painfully slow because, like the streetcars of Baltimore's past, they stop at every corner - about every 100-150 metres, compared to a generally accepted standard of 400m, visible in the bulk of European cities.
Unlike those streetcars, they have diesel engines that aren't very good at starting and stopping, and they're expected to violently pull in to the curb lane in order to get the hell out of the way of traffic, meaning the frequent stops slow them down considerably.
All of this is quite inadequate in a city in which much commercial activity and employment happens in centres well outside of the city, like the Woodlawn area containing a large mall and a large amount of government buildings, Towson with its important town centre in its own right.
So the Maryland Mass Transit Administration, the operator of Baltimore's city buses, desiring a quick solution to this sooner than they could build a hugely ambitious rail system, came up with the Quickbus concept, which is clearly inspired by the Los Angeles metro rapid. The two all-day quickbus routes (and three peak-time routes) are, like the Metro Rapid, ordinary buses that run in mixed traffic with the driver collecting fares, but that only make stops at major intersections, with the spacing between them varying between about 600m and 1.2km. They run every 15 minutes, with the all-day routes slightly more frequent at peak times.
The 40 between downtown and Woodlawn is the only route serving the whole of a main arterial, route 122, with local stop buses penetrating neighbourhoods on either side. As such, it's the only sensible way to get from downtown to Woodlawn, and worth waiting 15 minutes for. The other two corridors more questionable - the east end of the 40 to Essex via John Hopkins Hospital, and the 48 to Towson. They're questionable because they duplicate local buses for their entire length, which also run every 15 minutes.
As a basic frequency standard for a city that's assembling a network of frequent buses, a 15-minute frequency is a good starting point, but it's no mark of good rapid transit, which is what the quickbus is aspiring to. After all, if you're transferring between two routes at that frequency, you have up to 30 minutes of uncertainty built into your trip. This matter of frequency is where Baltimore runs up against the inescapable triangular geometry of public transport aims:
These cannot all be met without compromises. What baltimore is trying to do, in having quickbus services duplicating local buses is have a separate services, one to maximise speed (through widely spaced stops), and one to maximise penetration (through narrowly spaced stops), and it succeeds in this.
But in meeting those two aims, it compromises frequency, because to each of the two it can only allot a proportion of the total number of buses and drivers it has for the corridors, and each will only serve a proportion of the passengers. In this case, each bus runs every 15 minutes, where if the eight buses per hour in each corridor were evenly spaced, they'd be running every 7-8 minutes - a frequency where you can really start turning up at stops and knowing you won't wait long, and where you don't need to worry about missing one.
So can we balance these aims differently? Yes, I'd say we can, and my next post will be to set out such a proposal, and ponder the more difficult question of whether we should.


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