Sunday, December 1, 2013

Ashland Ave BRT 2, The report.

The city finally released their Environmental Impact report last week.
It is several hundred pages and I have been wading through it as fast as I can. They say it will have no impact, but that is what we expected them to say. So I will give my review so far.

First, 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.

 True.

They didn’t make it easy, but the rush hour traffic counts are there in
Appendix B-2: Level of Service Analysis
It’s labeled “Existing Volume Schematics” on pages 6-14 and it is in the form of a bunch of intersectional counts for every intersection.
They’re confusing, but to get a count for, say, the south side of any intersection,  you add all the vehicles in the north bound lane (inc turns) and the count in the south bound lane that travels straight and the south bound turns from the cross streets.

I did that and they showed that my seat of the pants AM rush traffic counts were right on the money. They indicate that compared to IDOT’s 2010 counts, they are 25% higher in the phase 1 zone (Cortland to 31st), 6% lower in the north section (Irving Pk to Cortland) and 13% higher in the south (31st to 95th). And when I estimated they would have to divert 650 car per hour in the rush, the actual number is more like 1000.
Even with these variations, IDOT’s counts were the closest to current conditions.

I tried to figure out which counts they were using for their planning. They show a map of what they thought it was at:
Page 12, (13 by screen count)
But it didn’t match any I had seen. They show traffic counts on Damen where it jumps over the South Branch and Stevenson in the 40,000 range. I can’t imagine that happening unless one of the other bridges was out.

It turns out that the numbers were based on CMAP’s Travel Demand Model, which was based on counts from as far back as 2002. They crunch the numbers and create a model that estimates the current conditions. Every so often they check it against the real world to see if it is accurate. This works well enough for the broad brush planning that CMAP does,  but it falls apart when it comes to pin-striping out what is going to happen at any one street.
I’ll get into that later. Right now, let’s go back to the intersection schematics.

The complex nature of the counts has some advantages. Because they counted every turn, on every intersection (down to alleys), you can get a reasonably accurate measure of how many automobile trips are taken on Ashland on the average rush hour.  This number would be analogous to the CTA boarding counts.

I added up the AM rush count  and found that  22002 vehicles enter Ashland Ave between Irving Pk and 95th each hour during the typical AM rush. I cross checked this by adding up the number of vehicles leaving. That total was 22342.

That is what you would expect. Roughly every vehicle that enters the road leaves at some point.

I ran the same calculations on their projected “Build Alternative Volume Schematics”. Those totals were 21666 vehicles entering and only 11940 leaving.

I am not sure how that is supposed to work. The increase in CTA ridership would only account for about 100 of the 1000 vehicles diverted each hour. The only scenario I can imagine where that would work is if half of the people who get on Ashland to take a 1-2 mile trip get stuck in traffic for over an hour.

To be fair, I don’t think this is part of an evil plan to turn Ashland into a 16.1 mile parking lot. I think they didn’t check the numbers because they just didn’t care. They were worried about what would happen when they magically cut the traffic rate in half and got rid of the left hand turns. All they cared about was whether CMAP’s model showed enough through lane capacity on the alternate routes.
Nothing in their calculations show what will happen when the 52 cars that used to make a left hand turn, eastbound onto Augusta are queuing up on Damen to make the same turn.

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.

True.
Go back to Appendix B-1: Regional Traffic Diversion Analysis

Down at the bottom they have (pgs 23- 28) they have maps of projected diverted volumes. Ogden has the second highest diverted counts. They blip over Elston and use Sacramento instead of California. The reason for these differences from my prediction is that they are using CMAP’s demand model that thinks these streets are already saturated.

Look at Appendix B-1: Regional Traffic Diversion Analysis page 11.
They have a chart called Table 1: Existing Conditions Results by NorthSouth Routes.
 Here they show something called the VMT.
VMT or “vehicle miles traveled” is the daily traffic count times the length of the road measured. It is simple enough. For roads of equal lengths, the road with the higher VMT has the higher average traffic counts.

Take another look at that chart. Particularly these three (the three highest)

Western Ave.                                                               VMT 306,429
Damen Ave.                                                                 VMT 322,336
Ashland Ave.                                                                VMT 264,626

They are operating with a model that shows Damen has a higher ADT than either Western or Ashland.
Damen is actually a couple of miles shorter then the others and this translates to Damen having a daily traffic count in excess of 22000 for its entire length. Damen only approaches 20000 in a few places. For the most part it is below 15000 and for a third of its length (Back of the yards) it is below 10000.
                
On page 12 they say:
“In reviewing the existing conditions travel demand model outputs, the VMT for Damen Avenue appears to be higher   than expected when compared with other parallel routes in the study area. However, the modeled VMT value is  not used in the  analysis, rather the relative change between Existing and Build Conditions is used, which is the best indicator for regional traffic diversion.”
           
So they noticed and ignored it. The VMT is the product of two numbers, one of which (the road length) is literally set in concrete. It didn't occur to them that the other (the modeled daily traffic count) is the very number they used to analyze the impact on every other route. It is a sad day when you hire a room full of engineers and not one of them has the good sense god gave a turnip.

Remember those maps at the bottom of “Appendix B-1: Regional Traffic Diversion Analysis”, well take another look. Damen at North Ave (based on IDOT’s counts) has excess rush hour capacity of around 375 vehicles an hour. They predict that it will only get 12 of the diverted vehicles during the AM rush. Western which has an excess rush hour capacity of less than 200, will see an increase of 348.
Why such a difference? Because of CMAP’s model they think Damen is way over capacity and Western is way under. They also think that Elston and California are over run with autos and that Sacramento Blvd is a good alternate despite the fact that a third of the phase 1 section winds its way through two huge parks.

Except for the actual time spent counting cars, the 7000 hours they spent modeling the traffic effects was a waste of time. It was based on data that was too coarse to be used in this way.

There are only three basic truths about the impacts on other streets
1,         Starting with the closest, all alternates will fill to capacity until all the traffic displaced from Ashland is absorbed.
2,         In as much as the average trip on Ashland is less than 2 miles, those alternates less than 1 mile away, will be under the highest pressure to exceed capacity. Increases on California and Kedzie will mostly be people who would normally take Western but have been diverted because of the congestion.
3,         The level of service, particularly on the two lane alternates, will decline in proportion to number of new left turn maneuvers in excess of available queuing capacity.

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.

Remains to be seen…
They are still referring to both the north and south segments, collectively, as phase two. However they always mention the south segment first.

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.

Remains to be seen…
The traffic rate is still higher up there. There is one possibility though. Reviewing the intersection schematics, I noticed something. The traffic rates spike between Belmont and Armitage. This leads me to believe that these are the result of people accessing the Kennedy.  Around 1000 cars turn onto or out of Webster and Armitage each rush hour. If a full time snafu at the Cortland lane reduction backs up into these two intersections, enough traffic may switch to an alternate ramp and lower the count to a more attractive number.
I am still holding to my prediction though.

So far I have two confirmed predictions and two pending, that’s a better batting average than Jeanne Dixon.

I feel emboldened to make a fifth prediction.
           
CMAP’s projections say that the building the BRT will result in 2% of the corridor wide VMT disappearing. A whopping 34000 Vehicle miles traveled. Don’t get worked up though, it works out to about 16 cars per typical rush hour on each of the 8 primary alternates.
Prediction #5
Geography and traffic lead me to suspect that the people accessing the Kennedy at Armitage and Webster are mostly from the east side of Ashland. Their access routes to the alternate ramps at Division pretty much suck. Elston is on the wrong side of the river, Racine doesn't go through and, Clybourn and Halsted squeeze them through a nasty choke point caused by the all the shopping at North Ave. These people represent 25% of the disappearing traffic and they will not disappear. Instead they will reroute outside of the corridor by using Clark and the Drive.

Paul K. Dickman

Coming soon
Ashland Ave BRT 3, The route we left behind.







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