Chicago should eject inefficient rail from expressway medians for toll express lanes

June 3, 2007
By Peter Samuel

Timothy W Martin secretary of the Illinois Department of Transportation 2003-2007, now a senior VP of CTE/Aecom said at a conference recently that Chicago doesn't need toll express lanes because it has something better - passenger rail lines in expressway medians. They carry far more people than the same space devoted to highway lanes, he claimed.

This is nonsense, but it's commonly held nonsense. An urban myth.

I went up to Martin afterwards and said: "You've got it wrong about the trains in the expressways. A lane of buses can carry more people than a rail line."

He scoffed saying I should look at the numbers.

I have. Wherever you crunch the numbers rail simply doesn't compete in hourly capacity with express buses. But here are the numbers for Chicago's Blue Line between O'Hare and the Loop which takes up a valuable 10m (33ft) down the middle of the Kennedy Expressway.

Chicago Transit Authority's (CTA) latest "Rail Ridership by Branch and Entrance" p5 shows 64.7k riders boarding or 32.4k riders in one direction on the average weekday in March. CTA's schedule shows they run 186 trains each weekday. They run a train about every 5 minutes in six peak hours and every 6 or 7 minutes in the middle of the day and about every 8 minutes in the evenings. 32,400 riders/186 trains is an average of 174 people on a Blue Line train. Maybe its 250 people per train in the rush hour and with 12 trains some 3,000 carried in the hour.

Cars can do that. An expressway lane with cars can carry 2,400 vehicles/hour and with a typical vehicle occupancy of 1.25 persons per car that's your same 3,000 persons per hour as the Blue line train. The darned train line is totally empty most of the time.

With pavement rather than rails you can do a lot better than just cars if you're in a corridor like the Blue Line between O'Hare Airport and downtown Chicago where there's a substantial demand for transit. Because both ends have large volumes of dense origins and destinations there's a demand for transit. But rail is a hopelessly inefficient form of transit. The 3,000 people per peak hour presently in a dozen trains could be carried comfortably in 100 buses.

100 buses per hour use about one eighth of the capacity of a highway lane. A bus lane can run 800 buses per hour. They've been doing something like that every weekday morning since 1971 in the Exclusive Bus Lane in the central tube of the PANYNJ's Lincoln Tunnel. And they collect tolls from all of them!

Over 3 3/4 hours in the morning peak they run an average 2,700 buses or 720/hour. That fits with the notion of a bus being the equivalent of about 3 cars. It matches up with expressway lanes all over the place capable of running 2,000 to 2,500 cars/hour.

Why do highways have so much more capacity than rail?

Two words: headway and passing.

The Blue Line is an inefficient rail line with headways of 5 minutes between trains. But nowhere are trains operated at closer than about 90 second headways. By contrast manually driven buses can operate comfortably at average headways of 4 or 5 seconds. 720 buses in an hour or 3,600 seconds is an average headway of 5 seconds. Rubber on asphalt provides so much better acceleration and braking than steel on steel. Indeed the limiting factor for road vehicles is not even acceleration/braking but human reaction time.

Lower headways and hence much higher throughput are likely in the future with driver assistance technology that can sense changes in closing rates with the vehicle ahead and adjust the brakes or accelerator - automated highway/intelligent vehicle systems. The advantage of highways over rail lines in capacity, already several fold, is only going to widen the gap further in the future.

The second reason roadway lanes are so much more efficient than rail lines is ease of passing. Dumb rail trains stop at so many more stations than express buses, so their average speed over a trip is a third or so lower than free flowing buses. The Blue Line train from O'Hare stops 14 times before it gets to the Loop downtown. Busway stops can be offline so only buses needing to stop pull off and stop, and others roll by. Railways with those clumsy mechanical switches can't afford express operation, so each train has to follow along behind the other, and stop at all the stops.

Buses in lanes managed for free flow would be more attractive than trains out of O'Hare and should attract more riders. That's because waiting times would be less. They would depart more often. And then they would get riders to their destinations faster because of the ability to run express bypassing stations. They could be routed more directly to their destinations by going offline into surface streets providing closer to door to door service.

Best of all, since the modest ridership of Blue Line trains transferred to buses would only occupy about one eighth of the capacity of a highway lane, seven-eighths of that capacity would be new capacity - available to be used by taxis, vans, trucks and ordinary motorists willing to pay a toll for a guaranteed free flow trip. You'd get 7/8ths of an express toll lane where at present there is many minutes of unused rail line between each train.

Chicago is hardly unique in having a wasteful, obsolete, inefficient rail system that absorbs vast amounts of taxpayer subsidies and does little for mobility. It is unusual in the amount of its rail system that runs in the median of major expressways. Long distances of median of the Kennedy, Eisenhower and Dan Ryan Expressways have median occupied by rail lines.

Removal of the rail equipment and replacement with managed toll express lanes would be a win-win proposition. Transit riders would get improved service. Motorists would get extra capacity after the small fraction of the lane needed for replacement buses was accounted for. And managed lanes would probably make money for the city instead of costing money - as rail invariably does.

The Loop rail lines should of course be kept for their historic value and as a tourist attraction. Serious transportation however is rubber tire on pavement.

We've invited Timothy Martin to respond.

TOLLROADSnews 2007-06-03


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