Public Interest Transportation Forum - http://www.bettertransport.info/pitf

Sound Transit light rail does not make traffic congestion better, and Prop 1 lets traffic delay become worse

Back in late 2000 Dr. Richard Harkness wrote an op-ed published by The Seattle Times titled "Sound Transit's light rail won’t make a dent in traffic congestion. So why build it?"  This essay stimulated Sound Transit's then chairman, Edmonds City Councilman Dave Earling, to write a responding op-ed essay in the same newspaper on December 26th 2000, page B5, titled, "Light rail: There will never be a better time." In that essay Chairman Earling opened with the memorable line, “Light rail will not ease traffic congestion. Yes, that’s a fact.”

Today, about six years later, the Roads & Transit project planners like to say that this $47 billion mega-package, over 60% of which goes into building 50 miles of light rail, would "ease congestion," a direct contradiction with Mr. Earling's words in 2000.  Even the Prop 1 ballot title opens with the words, "reduce congestion."

Turns out, Mr. Earling's fact is the one we should still believe.

The truth spoken by him about the performance of light rail in Seattle has been demonstrated recently in the computer modeling of future regional transportation performance conducted by Washington State Department of Transportation, with results released in a PowerPoint presentation to the Regional Transportation Investment District Executive Committee (pdf) on May 31, 2007. [Note: not all details of the study are revealed in the posted presentation; additional detail has been provided to PITF.] 

In the new WSDOT study, the congestion-reducing performance of the entire Roads & Transit package (Regional Proposition 1 to be put to a vote on November 6th, 2007) was modeled.  The package includes 50 additional miles of dual, two-way light rail track and 186 additional one-way lane miles of roadway.  What resulted from the study is a comparison of how severe congestion would likely be in 2028 both with and without the Roads & Transit package. The metric used is average daily weekday afternoon traffic delay measured in hours.  Afternoon traffic is often very bad around Seattle, as many know.

The Puget Sound region's traffic analysts already know from previous modeling that congestion will grow a lot between now and 2028, even with 125 miles of light rail and more road improvements than are specified in the RTID plan. Indeed, confirmation comes from the new WSDOT study:  the growth in traffic congestion by 2028 is expected to be 79% above today's level with the $47 billion Roads & Transit investment in place.  Specifically, the computer model forecasts that region-wide afternoon traffic delay grows from 106,582 hours to 190,952 hours in the 2006 to 2028 period. More details here. Some good news is that traffic delay would be 18% less bad than it would be if the Roads & Transit package were not constructed. (Supporters of the $47 billion go further to emphasize that afternoon traffic delay would be 25% less than it would be if both Roads & Traffic and the WSDOT investments from recent gas tax increases were not built. Since the issue in question is Roads & Transit, this comparison is disingenuous.) 

Bottom line: The growth in traffic delay would be substantial with or without light rail, as shown in the graphic.  The scale is marked in thousands of weekday afternoon daily hours in region-wide traffic delay as forecast by computer modeling.  Previous modeling released in Sound Transit environmental studies indicates that any improvement in traffic levels would not be discernable to those driving on expressways parallel to the light rail tracks.

(Note: The RTID staff director misinterpreted the WSDOT results in a presentation to a Post Intelligencer editorial board meeting on June 4, available in an audio recording as follows: "The result of our modeling has shown that we will have a 25% decrease in delay, in other words, you will not be delayed as much as you are today despite the growth in the population by the year 2027-28." 

(That's the same 25% as mentioned above, only comparing the change to today's environment is misleading. In actuality, 25% is an amount by which forecast travel delay growth is damped down from a counterfactual baseline, rather than how much the absolute level of travel delay drops from today's level.  Again, afternoon travel delay as measured in the WSDOT study rises by 79% from today to 2030, even with the $47 billion investment.

Back to reality: Population and the number of households are growing in the region, but congestion is expected to grow faster, despite light rail.  PSRC in a recent update of the Metropolitan Transportation Plan shows that daily travel delay per household is forecast to grow by 13% in the two decades of the Roads & Transit construction program.

Another study by PSRC looking at congestion out to year 2040 found that despite full implementation of Sound Transit's light railroad to the tune of 125 miles of track, traffic delay is expected to increase between 18 and 150 percent on expressways, and between 126 to 292 percent on arterials.  This means that delay on freeways might double, and delay on arterials is forecast to double (grow 100%), triple (grow 200%), or even quadruple (grow almost 300%).

Thanks to Dave Earling for the early warning!   Rather than easing road congestion, light rail provides a transit alternative to congestion for the fraction of people who ride it, yielding a few hundred thousand light rail trips out of 20 million daily trips in 2040.  Even with light rail, most regional transit trips will still involve a bus ride, according to the regional planning agency.

The Sound Transit light rail alternative would often include person-to-person congestion on crowded rush hour train station platforms, and when riding on escalators and elevators down into the subway tunnel, and while standing on trains that can carry twice as many people as there are seats.

A final question naturally arises:  When can we have planners present the region with a roads and transit plan that actually makes road congestion go visibly downward? 

Return to the Public Interest Transportation Forum home page.

Last modified: February 07, 2011        

Hit Counter