Reston Spring

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Wednesday, July 18, 2012

News Flash: Drivers Avoid Tolls, Sightline Daily, June 28, 2012

Over the past couple of months, we have detailed how the explosive growth in tolls in the Dulles Toll Road as forecast by MWAA's traffic and revenue forecaster, CDM Smith, will result in the diversion of a substantial volume of traffic to other local roads.  The diversion derives from two sources:
  • The toll increases become less affordable for drivers and their "value of time" calculation (a CDM Smith turn of phrase--price elasticity of demand in economic-speak) makes them change their preference for using other roads.
  • Over time, the growth of jobs and population along the toll road corridor sees an unmet potential as many of these new potential toll road users divert to other roads, switch to some form of public transit, or work from home.  
The results as we have calculated them suggest the following near and long-term consequences:
  • Next year, if tolls double as forecast, CDM Smith forecasts that toll road use will decline by 18%--or 36,000 trips per day given the more than 200,000 daily trips on the toll road according to a survey by CDM Smith.  Since there will be no Metrorail and Fairfax and Loudoun County have no plans to expand bus transit for the one-year gap before Phase 1 of the Silver Line is in service, that means 36,000 trips per days on area roads.
  • In 2050, more than 100,000 trips per day will be diverted to local roads by our calculations.  That allows for one-quarter of the future growth in employment and population in the "prime market area" (roughly the area north of Rt. 50 and east of Rt. 15--Leesburg) to take public transit (bus & rail) or work from home.  The job and residential growth estimates are those by CDM Smith's socio-economic forecaster, Renaissance Planning Group.  
Here's what that result looks like over the next four decades:

 


Now it appears that we are not alone in forecasting huge traffic diversions from exorbitant toll increases.  Sightline, a non-profit Washington state-based planning group, reports in an article by Clark Williams-Derry in Sightline Daily that Seattle in facing the consequences of major toll increases for a major area tunnel.  Here is how his article, "News Flash: Drivers Avoid Tolls," begins:
For Seattle traffic-watchers, Mike Lindblom at the Seattle Times has the most important story of the month: the news that a new state traffic study predicts that high rush hour tolls on the Alaskan Way Viaduct tunnel will divert 9,100 cars into downtown Seattle during the afternoon commute. For those of you who are counting, that’s a diversion rate of about 42 percent.
The Times editors considered it a bombshell. It was the day’s top story, above the fold, with a huge headline.
But here’s the thing: it’s not really news. Well, it’s only sort of news. I mean, there really was a new tolling study on the Viaduct, and it really did predict that lots of drivers would avoid the tolls by driving on surface streets. Yet the new study reached almost exactly the same conclusion that WSDOT itself reached last year.
Williams-Derry makes an important observation about why the insight--provided a year earlier--was largely ignored:
I suspect it’s part of a regrettable human foible: in context of a political campaign or a hotly contested public policy controversy, people view facts as weapons for winning arguments, rather than as a means for discovering the truth. When emotions run hot, the press tends to evaluate factual claims for how they’ll affect each side’s political fortunes, not for whether they’re important or true.
Now that the the political controversy has subsided, the press can once again cover the facts about the Viaduct a little more rationally: weighing their validity and exploring the implications. Better late than never I suppose. Still it’s a shame: just when the public was in greatest need of solid facts, the press seemed more focused on the politics than the substance.
In the context of the Dulles Toll Road, we have seen some reporting on the toll increase-traffic diversion phenomenon from local newspapers, particularly Patch.   Still, most of the media's focus has been on the comments of politicians and advocates (pro or con, left or right) rather than on the facts--more accurately, a balance assessment of the available data--as Williams-Derry suggests. 

So while the Fairfax County Board of Supervisors cared not a whit about these assessments nor conducted any of their own on the implications of higher tolls, the Loudoun Board considered but disregarded the traffic and other implications of huge toll increases on BOTH the DTR and the Greenway, and the state of Virginia has not even begun to fathom the implications for its transportation budget planning, we now face a situation where all parties are flailing to find funding to lower tolls and minimize the impact of diversions.

When politics trumps rational and systematic planning and problem solving, the community--local, county, state, and even federal--pay the consequences of poor decision making, in this case, for at least four decades.  

4 comments:

  1. I think the graph (and accompanying story) is highly misleading to the average reader, especially for the period decades from now when the whole company-commuter-public infrastructure model is likely to be different than it is today. Increasingly limited road capacity will demand change.

    “Vehicle trips” are not only affected by DTR tolls and population growth, but also by commuter behavior. Never mentioned in the story are the traffic moderating influences of increased telecommuting, ridesharing & public transportation incentives, and satellite work centers, just to name a few of dozens of examples. In short, every new or DTR diverted commuter over the 40 year period will not necessarily translate into another vehicle on the road as the story and graph suggests.

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  2. Anon--Thanks for your thoughts.

    I agree with you that future transportation-work modes will be different than today. Indeed, the graph you criticize depicts that change: We expect 25% of those in the "primary market area" (as defined by CDM Smith, not us) will NOT use the DTR because of the types of reasons you outline. That would include about 10% who will take Metro (a generous forecast compared to any others available) and 15% for all the other reasons. (Note: Most forecasts put current work-at-home in our area at about 7%, so we've allowed for a substantial expansion there. Of course, with Amazon, eBay, and the rest, more and more future shopping will be from the laptop/iPad vice visits to the mall as well.)

    I tried to make this clear in both the narrative and even the legend to graphic, but I apparently wasn't sufficiently clear. Sorry.

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  3. What is your confidence level that the region will in fact see 103,000 vehicle diversions/day in 2050? I am wondering about the accuracy of the predictive algorithm and assumptions used in deriving a number nearly 40 years from now. I am not trying to be contentious, but just curious.

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  4. You raise a good point, Anonymous. In fact, it is one we have raised with MWAA and its well-paid consultants who made the Dulles Toll Road traffic and residential and job growth projections upon which we built our diversion forecast.

    In particular, in a meeting with MWAA's CFO and key consultants, we pointed out the value of an estimative range for their various key findings, including the use of a Monte Carlo simulation. CDM Smith--the traffic & revenue forecaster--has used MCS in other forecasts in Texas, for example. We were told that, in the case we cited, it was a private "for profit" toll road and, therefore, they wanted to know the "up side" of the baseline forecast. I still don't know why they didn't do so because it would be more realistic.

    Elsewhere in this blog, you will find a paper we wrote on the HUGE uncertainty in traffic and revenue forecasts. (See our "Wilbur Smith . . . Plenty of Room for Error" paper listed on the right under the "RCA Reston 20/20 Papers." Warning: It's 100+ pages long.) Suffice it to say, forecasters, including CDM Smith/Wilbur Smith, have erred by more than 100% ON AVERAGE in the first five years of their forecasts for new toll roads. The problem is not as severe early on for established toll roads, such as the DTR, but grows as much over time. As a result, we see little value (& great difficulty) in generating a confidence interval for our little traffic diversion based on CDM Smith's forecast.

    The range could be between 50K and 200K trip diversions in 2050--and that's just considering the error range in the underlying consultant forecasts. We, of course, no doubt made our own--but we haven't been paid nearly as much (or at all).

    Hope that lengthy answer helps. The forecasts are not very reliable long term, but they are all we have.

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