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/