J. Chisholm wrote:
Aidan Stanger wrote:

Does TfL (or anyone else) try to estimate the value of bus lanes
before installing them? If so, what criteria do they use?

Am I right in thinking London's most expensive bus lane so far was
the one on the M4? Am I right in thinking the consensus now is
that it's a white elephant?

That's not what studies of this lanes say:

http://news.bbc.co.uk/1/hi/uk/1120542.stm

"It has now been given the government's seal of approval after a
case study showed it had cut rush-hour journey times for both cars
and buses."

But what that study (or at least the news report based on it) failed to
answer was how much of the benefit has arisen from changing the speed
limits. Before the bus lane was introduced, the limit was 70 mph on the
3-lane section, then 50 mph on the elevated section. When the bus lane
was introduced, the limit changed to 50 mph (now 60), and 40 on the
elevated section. I suspect that much of the benefit has arisen from
the lower speed limits, for the same reasons that the variable speed
limits on the M25 have improved journey times.
--
Richard J.
(to e-mail me, swap uk and yon in address)