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Chapter Two
Lessons from the Case Studies

Road construction may deliver few benefits to drivers.

Building new roads and expanding old ones is certainly necessary in some instances, but the case studies in this report illustrate that widening roads offers little relief for current drivers, even when the growth in traffic is taken into account. The construction itself can create so much delay that it will take current motorists years to make up for the time they wasted in the construction zone. The widened, free-flowing highway will deliver such meager time savings that the patience of regular road users who sat through the construction will not be rewarded. For the projects analyzed for this report, the "break-even" point for current users ranged from a low of more than two years after project completion in Nashville to never in the case of the Springfield Interchange in Virginia.

While the roads deliver only small time savings to current drivers, they do permit many more motorists to use the facility. In the case of Route 29 in Trenton New Jersey, traffic volumes are expected to jump by 60 percent. In addition to population growth, one reason for the increased traffic is "induced travel," which occurs when road capacity is expanded and drivers flock to the new road hoping to save time. Our case studies show that while construction projects are often billed as relieving congestion for those currently suffering through it, what they actually do is allow more traffic and more driving. Current highway users get little benefit.

Traditional traffic planning fails to measure what is most important to citizens: their own driving experience.

While motorists expect construction projects to make their commute faster and easier, highway engineers view them differently. They look at the "capacity of a transportation facility…[and] the quality of flow" through that facility.¹⁸ They judge projects in terms of Average Daily Traffic (ADT), Maximum Density (passenger cars per mile per lane), Maximum Flow Rate (passenger cars per hour per lane), and the Maximum Volume to Capacity Ratio. In essence, what they measure is how many cars they can pack onto a highway before the highway reaches "Level of Service F," the engineering shorthand for highway failure.

Transportation planners rarely give more than a cursory consideration to the congestion individual motorists will face during the construction period, and they rarely calculate how a project will affect the individual driver. They also often fail to take into account the new traffic the project will create. When asked about these impacts, officials often have no answers. But this study finds that these impacts can greatly detract from the ultimate worth of a project. As a result, road projects that succeed in increasing capacity, can fail when it comes to significantly improving the lot of individual drivers, especially when construction delay is a factor.

Widening roads allows more traffic but not significant time savings

Construction only addresses one part of the congestion problem.

Road builders fight congestion with the tool they know best: road building. But congestion is a larger problem that demands comprehensive solutions. Population growth is often cited as the underlying reason for the need to increase road capacity. However, in the past 15 years, road building has more than kept up with population growth in metropolitan areas: the number of miles of roadway per person has increased by nine percent. But the amount people drive has grown far faster than the population, with daily miles traveled increasing two to five and a half percent per year since the 1950s.¹⁹ People are driving farther, making more trips, and driving alone more often.

This increase in driving is in large part a result of sprawling, unplanned development that requires many car trips. Far-flung subdivisions and office parks isolated from stores and schools leave residents no alternative to driving. One of the unintended consequences of this growth pattern has been a steadily increasing number of short vehicle trips that has served to clog local streets and freeways with traffic and increasingly frustrate residents and workers. And as this report shows, making roads ever wider may do little to help those who must use the roads every day. It seems clear that other approaches are necessary to give Americans the congestion relief that they seek.

Some representatives of the road building industry have suggested that increased road capacity is necessary for economic growth and that failing to build more roads would retard the growth potential of the U.S. economy. However, other studies indicate that road building in areas that already have an extensive road network may have very modest effects or do no more than shift economic activity from one location to another.²⁰ In addition, a major study done for the British government states that "any contribution to the sustainable rate of economic growth of a mature economy, with well-developed transport systems, is likely to be modest."²¹ The study concludes that generalizations made about the effects of transportation on the economy are strongly dependent on local circumstances and conditions.

Additional highway space can mean additional traffic.

For this study, we used state Department of Transportation figures to estimate projected time savings delivered by the roads studied. But these figures may be very optimistic, because often these projections ignore a phenomenon known as induced travel. New and wider roads tend to generate new traffic. People make additional trips, travel farther, change their routes or change their time of travel when new capacity is made available on highways. In the long run, new residential and commercial development takes advantage of the improved accessibility resulting from road widening, and this new development generates new trips and more traffic. Induced travel means that roads often fill-up long before their projected road life-span.

State highway departments generally expect good traffic flow for ten to twenty years after a construction project is completed, and we used these projections in our case studies. But a growing body of evidence shows that the increased highway capacity can be filled up in as little as a quarter of that time, as induced demand generates additional traffic. According to the Federal Highway Administration, improved travel speeds may "induce" an increase in traffic. Using a conservative FHWA estimate of the impact of induced travel²², an STPP analysis found that by the year 2011, a mere decade after construction is completed, average speed on I-15 in Salt Lake could drop to 45 mph. This is lower than the average in 1996, before construction began.