Initial intersection crash analysis for Milwaukee Avenue

Slightly upgraded Chicago Crash Browser

This screenshot from the Chicago Crash Browser map shows the location of bike-car collisions at Ogden/Milwaukee, an intersection that exemplifies the yellow trap problem the city hasn’t remedied.

List of the most crash-prone intersections on Milwaukee Avenue in Chicago. Using data from 2007-2009, when reported to the Chicago Police Department. Dooring data not included on the bike crash map. I used QGIS to draw a 50-feet buffer around the point where the intersection center lines meet.

Intersecting street (class 4*) Bike crashes
Chicago Avenue (see Ogden below) 12 (17)
California Avenue 9
Halsted Street & Grand Avenue 7
Damen Avenue & North Avenue 6
Western Avenue 6
Ogden Avenue (see Chicago above) 5 (17)
Ashland Avenue 5
Diversey Avenue 5
Fullerton Avenue 5
Elston Avenue 5
Augusta Boulevard (not class 4) 5

Combine the six-way (with center triangle) intersection of Ogden, Milwaukee, Chicago, and you see 17 crashes. Add the 6 just outside the 50-feet buffer and you get 23 crashes. Compare this to the six-way (without center triangle) at Halsted, Milwaukee, Grand, where there’s only 7 crashes.

What about the two intersections causes such a difference in crashes? Let’s look at some data:

Ogden, Milwaukee, Chicago Halsted, Milwaukee, Grand
Automobile traffic Approx 58,000 cars per day Approx 50,000 cars per day.
Bicycle traffic Not counted, but probably fewer than 3,100 bikes More than 3,100 bikes per day*
Bus traffic Two bus routes Three bus routes
Intersection style Island; three signal cycles No island; one signal cycle


Traffic counts are assumed estimates. Counts are taken on a single day, either Tuesday, Wednesday, or Thursday. Bike counts at Halsted/Milwaukee/Grand were actually taken on Milwaukee several hundred feet northwest of the intersection so DO NOT include people biking on Halsted or Grand! This means that more than 3,100 people are biking through the intersection each day.

Intersection style tells us which kind of six-way intersection it is. At island styles you’ll find a concrete traffic island separating the three streets. You’ll also find three signal cycles because there are actually three intersections instead of one, making it a 12-way intersection. Also at these intersections you’ll see confusing instructional signage like, “OBEY YOUR SIGNAL ONLY” and “ONCOMING TRAFFIC HAS LONGER GREEN.”

These intersections are more likely to have a “yellow trap” – Ogden/Milwaukee definitely has this problem. The yellow trap occurs at that intersections when northbound, left-turning motorists (from Milwaukee to Ogden) get a red light but they still need to vacate the intersection. Thinking that oncoming traffic has a red light but are just being jerks and blowing the red light (when in fact they still have a green for 5-10 more seconds) they turn and sometimes hit the southbound traffic. The City of Chicago acknowledged this problem, for bicyclists especially, in summer 2013 but as of November 2014 the issue remains.

Here’s a more lengthy description of one of the problems here as well as an extremely simple solution: install a left-turn arrow for northbound Milwaukee Avenue. The entire intersection is within Alderman Burnett’s Ward 27.

Source and method

I can’t yet tell you how I obtained this data or created the map. I’m still working out the specifics in my procedures log. It involved some manual work at the end because in the resulting table that counted the number of crashes per intersection, every intersection was repeated, but the street names were in opposite columns.

Crash data from the Illinois Department of Transportation. Street data from the City of Chicago. Intersection data created with fTools in QGIS. To save time in this initial analysis, I only considered Milwaukee Avenue intersections with streets in the City of Chicago centerline file with a labeled CLASS of 1, 2, or 3.

My essential QGIS plugins

Plugins for QGIS I use most often.

All of these can be installed automatically by QGIS. Click on Plugins>Fetch Python Plugins. Then search for the plugin, click on its name, and click Install Plugin. Few plugins require a restart.

  • MMQGIS – Great for working with CSV files; also merges layers (even if they have differing attributes); has various other useful functions, including converting string data to float data. Has Voronoi diagram function (takes a long time to process).
  • fTools – Replicates some of the most basic geographic tools in ArcGIS, like Clip, Dissolve, and Reproject. Can also add X/Y values to point attribute tables that are missing them (if you want latitude/longitude, you must reproject into a coordinate reference system first, like WGS84 [EPSG: 4326]). Unfortunately, there’s little information on what each fTools function does. Below are descriptions:
    • Extract Nodes – Create a point at each intersection of vertices.
    • Basic Statistics – Generate arithmetic statistics for fields, same as statistics function in ArcGIS. Great for quickly understanding the extent of values in a field (especially numeric values), like mean, max, min, standard deviation, and number of unique values.
    • Nearest Neighbour Analysis – More details here.
    • Geoprocessing Tools>Dissolve – Combine features based on a shared attribute. For example, all features with an identical STREET_TYPE be combined into a single feature. For example, all “Avenues” will become one feature and all “Boulevards” will become a second feature. Only works on polygon layers.
    • Descrição em português
  • Table Manager
  • Open Layers – Embed Google, Yahoo, Bing, and OpenStreetMap layers in your map. See my example.

Where I went in 2009 through 2011

I think my trip to San Francisco this past weekend for visiting friends and Transportation Camp West winds up over a year of domestic and international travel. This post links you to all the recap entries and Flickr photo galleries for the awesome cities I traveled to, rode the train in, and biked through.




Approximate 2009 travel distance: 3,792 miles*







Approximate 2010 travel distance: 17,515 miles (does not include intercity train trips)*







Approximate 2011 travel distance: 8,271 miles (does not include intercity train trips and one car trip)*

*Travel distances exclude biking, walking, and trips on transit.

Ideas for CTA’s incoming 5000-series train cars

Update: Stay current on this topic at Grid Chicago. Latest post was on July 25, 2011, about the latest rail car order
The Chicago Transit Authority (CTA) is not exactly seeking feedback from the public at this time about the Bombardier-built 5000-series train cars it’s testing now. But this is our one chance to make these trains eve better.
  • No beige. This is not the 1980s.
  • The seats shouldn’t define individual spaces if they’re going to be longitudinal. Seat cups mean “If you fit into one, then you fit into one. If you take up 110% the width of one, you now take up two.” But if they were benches like in New York, people would only fill exactly as much space as they take up.
  • The end caps should be a different color plastic, not something intended to look like the aluminum siding from afar, which then up close is clearly nothing more than a plastic approximation. Even without redesigning the endcaps, the dye color being darker and some reflective striping (to make them not vanish into the night if the car has no lighting), would make them look ultra modern.
  • Remove the modesty panels. They serve little purpose in this day and age.

If you have ideas, leave them in the comments or email the Chicago Transit Authority.

Written in conjunction with Better bicycle storage on trains.

Photo by Jeff Zoline.

Top keywords people use to find Steven can plan

Being a “webmaster” (should we retire that word?) is a lot of fun. There are so many tools that make being a webmaster easy and enjoyable.

The best tool ever – statistics! Also known as analytics. With statistics, you get to learn what words and phrases people searched for and found your website.

Day after day, the same keywords show up in my statistics:

David Bryne, Luann Hamilton, Randy Neufeld, and Jacky Grimshaw (in the back) were the panelists at “Cities, Bicycles and the Future of Getting Around: A Special Urban Sustainability Forum with David Byrne.”

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