Friday, December 13, 2013

Ashland BRT Left Turn Accomodation

Currently there is some controversy about the potential elimination of left turns in the Ashland BRT (Bus Rapid Transit) proposal by the CTA (Chicago Transit Authority.) Let me say at the outset that I support the Ashland BRT no matter the specific design. I would, of course, prefer the design that meets all the current gold standards of BRT design. The primary ones are: 1) an exclusive dedicated bus lane, 2) fare collection before boarding, 3) bus driver control of stop light signals. It is worth getting it right on Ashland as Ashland paves the way for other BRTs such as Western Avenue.

However, I do feel that it is important that as many stake-holders as possible sign on to all critical design elements. Therefore, in order to appease demands of left turner lobby, I would support such outside-the-box approaches as the one I present here:


It is not to scale. Everything is eye-balled. When push comes to shove there may well be some element that simply will not fit.

The out-of-the-box element that makes this design work is the combination of both left and right turns from a single lane (orange in the diagram.)  Left turns would be allowed only during signals. Right turns would be allowed anytime but would be constrained by the presence of left turners. I get that combining the turning lanes into one would be less than ideal. But transit riders have lived with less than ideal design for a long time. My argument is that for 50 years automobiles have been catered and deferred to with street design, even where they don't deserve it in urban settings. I say it is now time to defer to transit needs over car needs in those settings.

The major drawback with this design is that it costs more because two BRT loading stations are required instead of one. That means all feature elements for transit use, fare collection, turnstiles, roofing, signage and the like must be duplicated. However, a major additional feature with this placement of the two stations is that it can be shared by the local bus allowing for easy off / easy on transfers from a local bus to a BRT bus going the same direction.

Since the local bus would pull into the car lane for loading and unloading, the BRT bus could pull ahead. Indeed such a design would make it practical to place the BRT stations at one mile separations as users could easily change buses.

It is my contention that the extra costs of additional stations should come from the streets and highways budgets because cars are the ones benefiting from the ability to turn left. If it were up to me as a very irregular south-of-Irving Ashland driver I'd say can the left turns as I can live without them.

UPDATE 12/16/13: Interestingly the international standard for BRT's have a score that is highest for BRT's that allow no left turns. Another reason to ban them -> http://www.itdp.org/microsites/the-brt-standard-2013/brt-basics/intersection-treatments/

4 comments:

Bob said...

Left-turn-arrows are an abomination and should be rarely used anyway. Look at any intersection that now has left-turn arrows: when the left turn arrow is active pedestrians are halted in all direction. In winter, pedestrians must wait so drivers in their heated cars can drive more quickly. In summer, pedestrians must wait so drivers in their air-conditioned cars can get moving faster. Should seniors, pedestrians, children, handicapped and more all need to tolerate this for cars?

Jeff Wegerson said...

Excellent point! Of course, ideally, all traffic would be separated with their own exclusive networks. Indeed inside of very large buildings transit is separated from pedestrians and cars are banned. Transit is the elevators and pedestrians have their own stairs. But we are not there yet. So we must get there from here. Since BRT is such a huge step, yet achievable, I believe that it behooves use to once again make some compromises. Only, though, if cars are actually willing to compromise as well. In this case they compromise by having to share a turning lane. And since it only takes one left turner to freeze the right turners behind them, pedestrians will have free reign on both the crosswalks. So it might not be so bad a compromise for pedestrians in this case to have a left turn light.

Elliott Mason said...

I don't really see how this could work -- first off, the local busses are going to be the usual CTA busses we have now, they only have a door on one side, and it's not the side you've got them pulling up to 'the station' with.

Second, how does it even help to have two stations like that on the sides instead of one in the median? It uses up the same width of street no matter where in the street you put it, and by making one set of uninterrupted asphalt lanes so much longer than the other, makes it a much more hostile street to cross on foot.

I guess I don't see the advantage. YOu can still swipe the parking lane for a left/right dedicated turn lane if you want without moving the station median ... though personally I have doubts about the utility of a left-right combined lane.

Here's a non-unusual hypothetical situation. It's a red light on Ashland. The first and third cars in the turn lane wants to go left. The second car in the turn lane wants to go right. The left turn light goes on -- the left turner turns, no problem. The right turner DOES NOT (and should not, because the lefters from the other direction are using the side street). Second Car correctly and legally waits for their green, then turns. Now Third Car has to wait an entire light cycle, jamming up anyone behind him who wants to make a right.

How will this work at all?

Jeff Wegerson said...

@Elliot - 1) We don not have to assume that the local buses will be the same standard CTA bus. It could be a special regular size bus with exit doors on the left.

2)The reason for two stations is so that they can be slightly narrower for one and two so that both a regular bus and a BRT bus can serve the station at the same time without slowing the BRT bus.

3) Uninterrupted asphalt? Actually the painted walkway perpendicular to the cross street that allows access to the station interrupts in a manner to make it less hostile to pedestrians. Not perfect I agree but remember allowing left turns is the cause of the hostile pedestrian environment not my solution to cater to them. Don't blame the victim here.

4) Your hypothetical. Yup. You got that right. But see, I don't really care. When I drive places I either avoid those situations or I wait patiently. It's life in the big city, eh?