This is about the CTA’s Bus Rapid Transit plan. An idea to
run busses like trains up and down existing streets.
If you are unfamiliar with it, you can read about it here:
If you are not from around here you should probably just
skip over this one. It is pretty dry and full of technical gibberish and location
references that are pretty specific.
I have been shooting my mouth off and now it is time to put my
predictions down in writing.
The Phase one of the BRT plan, in its current incarnation,
involves Ashland Ave
between Cortland and 31st
St. , but in the future, the plan is for it to run
all the way from Irving Park to 95th .
At the start, there were eight
possible systems, four different configurations on two different streets. Ashland
and Western. The one they have settled on is this:
They will turn the two inside lanes
of Ashland Ave (a four lane
street) into Bus only lanes, using the median like an El platform.
They will reduce the number of
stops to two per mile (because they realize that it is not the traffic that
slows down busses, it’s the passengers) and eliminate virtually all the left
turns. This will cost $10,000,000 per mile ($161 mil total) not including the
new fleet of busses with their doors on the left side.
The city’s presentations have all
been sweetness and light, and pretty much devoid of any actual facts that
haven’t already been spun tighter than a violin string.
Owing to this, my first analysis
was based on the only real facts I had, existing traffic volume and road
capacity.
Yes, roads have a capacity and a
pretty well defined one. According to IDOT (the people who control the purse
strings) a 2-way urban arterial road has a capacity of 1250 vehicles per
hour for a two lane (one in each direction), 1250-2050 for a four lane, and 2050-2900
for a six lane. Roads are supposed to be built so that their capacity should
meet or exceed their Design Hourly Volume (DHV). DHV represents a fairly bad
rush hour, but not the worst ever.
The most recent traffic count I
found was from IDOT in 2010. It said that the Average Daily Traffic (ADT) on
most of Ashland in Phase one was 27,200
vehicles a day.
CDOT has more in depth counts from
2006. Not only are they older, but 2006 was the year of the Dan Ryan
reconstruction (on the south) and the North Ave
bridge removal (on the north). In my opinion these numbers were too skewed to
be of any value. They were also much, much higher than the state’s numbers.
To obtain a DHV from the traffic
counts, you can multiply the ADT times something called the K factor. This is
nothing more than an approximation of the ratio between the ADT and the hourly
count for the thirtieth highest traffic hour of the year. Typically, urban
arterials have a K factor of around 9% but on a street like Ashland ,
that still has a lot of traffic after midnight ,
you can make a sound argument for a K factor in the 7% range.
So, we take 27200 x .07 = 1900 DHV
existing. If you want to switch this four lane into a two lane, you have to get
rid of 650 cars during rush hour or about 10,000 vehicles a day.
Where are they gonna go?
Figure half of them will take the
biggest alternate (Western) and another quarter of them will take the nearest
alternate (Damen) and the rest will scatter around. 325 cars at rush hour will
put Western near or above the 2050 capacity for a four lane. That’s OK, you can
put in a rush hour parking ban.
Damen, up here in the Wickerbuckukie
Parktown Village Grand
Ave. the count is high enough that a similar ban would
probably be needed.
Realize that a parking ban will
also get rid of the bike lanes. The difference between the minimum width of an
auxiliary lane and the minimum width of a parking lane is the width of a bike
lane.
At first glance, it’s doable with
rush hour bans on Western and parts of Damen.
Next, I wanted to cross check using
few scraps of actual data the CTA let out, mostly Traffic Mode Share.
This is not the same as ridership.
It is the ratio between the number of people on busses to the total number of
people traveling the road. As a ratio it has two variables. To increase the TMS
you can either, double the number of bus riders and let the car traffic stay the
same, or you can maintain the same number of riders and get rid of 15,000 cars.
The reality is somewhere in between,
and that is what I wanted to find out.
The CTA said that their current
transit share might be as high as 15%. Working backwards from their different Ashland
configuration comparison pages, they said that 17%TMS represented a 21%
increase, 19%TMS for a 36% increase 23% for a 64% increase and 26% for a 46%
increase. I think that last one (the current proposal) is actually a typo.
Otherwise they all represent a current mode share of 14%. The Cta repeats this
number on this infographic.
If transit share is 14% then auto
share is 86%, and 27,200/.86 = total of
31,628 with of a daily average transit passenger load of 4428. This would
represent all the bus passengers passing through any single point on Ashland
Ave. on an average day and is analogous to ADT.
An earlier report from the
metropolitan planning council said that you could expect an increase in
ridership of 14.3% from BRT schemes. So, I tried that first.
4428x1.143 = 5061 passenger load
with BRT. The current plan for Ashland
says that it will capture a 26% Transit Mode Share. 5061/.26 = 19,466 total
travelers minus 5061 on busses leaving 14,405 in cars or a loss of about 13,000
cars a day (only 600 of which could be accounted for by mode switchers). This
seemed a little ambitious, so I increased the new passengers to 30% and ran the
numbers again.
They gave me a passenger load of
5756, total travelers of 22140 and an ADT of 16390, or a loss of about 10,000
cars a day. This is the same as my road capacity calculations.
At our most recent presentation
from the city, they put up a graphic that projected an increase in ridership of
29%. I am pretty sure that I nailed down the assumptions they were dealing
with.
CDOT has been doing new traffic
counts and they have spent 7000 hours collecting and modeling the counts.
Myself, I performed a few seat of the pants AM rush counts and they indicated
that my assumptions about either the ADT or the K factor were way too low. I
suspect this is correct. Why would they need 7000 hours to model the traffic if
it wasn’t?
The city’s traffic analysis is due
out next month, so now I’ll make my predictions.
Prediction #1
The rush hour traffic count will
come out higher than expected, and the parts of the plan the CTA won’t want to
talk about will include rush hour bans on all of Western and Damen (with loss
of bicycle lanes) and probably parts California ,
Kedzie and Halsted.
Prediction #2
If phase one gets built as planned,
the route of Elston to Ogden to California
will turn into an unintended bypass. This will piss off the people on Fry
St. to no end, because everyone will be using
their street to dodge the traffic snafu in the Elston-Milwaukee-Ogden
interchange.
Prediction #3
If phase one ever gets built, phase
two will be the southern portion. Traffic on Ashland
and Western are 10% lower down there and shouldn’t present a problem.
Prediction #4
Phase three, will be from Clybourn
to Irving Park and it will never be built. Traffic on Ashland
is 25% higher up there and all the alternates are near capacity.
Barring thermonuclear war in the Middle
East , they will not be allowed to reduce that stretch to two
traffic lanes. To build it as a four lane could not be done without fulltime
loss of the medians and all street parking, or widening of the roadbed. That would
involve moving storm drains, streetlights, signs and stoplights and would
substantially increase the per mile cost.
Understand, I am pretty much a pro
transit kind of guy. I admit to owning a car, but it is thirteen years old and
only has 37,000 miles on it. That is because I take CTA as much as possible.
I think BRT is a great idea! I
would have piped up sooner, but one of their proposals for a curbside BRT on
Western would, travel just as fast as this plan, carry just as many new riders
as this plan, cause negligible traffic impacts, and cost 55 million dollars
less.
Frankly, it never crossed my mind
that anyone would be crazy enough to not choose that one.
