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 January 1, 1998

Transportation ‘half-truths’ don’t always hold up

I’ve noticed transportation issues (highway congestion, public transit, etc.) are a little like sports (hockey, football, etc.). Everyone is an expert, but no one agrees with anyone else.

One reason we debate transportation so much is we rely too much on a number of common half-truths. These cause trouble precisely because they are at least partially true. Let’s look at some of these half-truths and see how they hold up under scrutiny.

Traffic growth is caused by population growth.

During the 1980s, Colorado’s population grew by 13 percent. In the same decade, our daily roadway traffic grew by 39 percent. The regional forecast is for traffic to increase at a rate at least twice as fast as population between now and 2020.

Who is causing our traffic? You and I are. We all are driving more than we did in past decades. Average per capita vehicular travel in the Front Range has grown from 16 miles per day in 1970 to 25 miles today. We could easily top 30 miles per day within a few years.

This increase in driving is due to two causes: demographic/economic trends and patterns of urbanization. Most of the relevant demographic/economic trends have peaked and will contribute little to traffic growth over the next two decades. The primary cause of increasing vehicular travel between now and 2020 will be our land development patterns.

Population growth is one cause of increasing traffic. But it is not the only, or even the primary, cause.

Building more roads will alleviate congestion.

In most cases a short-term reduction in congestion results from adding roadway capacity. But this is only part of the story. Another, potentially more important part of the story has to do with “latent demand” and “induced traffic.”

Front Range drivers today avoid a certain amount of travel because they dislike driving in heavy traffic on congested roadways. How many times have you heard someone say they no longer go to the mountains to ski because the traffic on Interstate 70 is so bad? The trips we would like to make but don’t represent “latent demand for travel.”

When roadway capacity is increased, some of the latent demand for travel is converted into “induced traffic.” In other words, people respond to roadway widening by making trips they previously avoided. Or they resume driving at peak periods. Or they change routes to take advantage of the new roadway. Research indicates about 60 percent to 80 percent of added roadway capacity is consumed by induced traffic within two to five years.

Over the long term (10 to 15 years) the remaining 20 percent to 40 percent of new roadway capacity is consumed by new traffic associated with land use changes. (Would the ongoing development of southern Weld County be occurring if there were no Interstate 25?)

New roadway lanes will reduce congestion. For awhile.

Public transit, bike paths and sidewalks will alleviate congestion.

This depends on your definition of “alleviate.” For the foreseeable future, worsening congestion is inexorable.

Investments in the primary modes (transit, bicycling and walking) — no matter how massive — will not reduce, or even prevent increases in, congestion. Even at the highest potential levels of implementation, these strategies — taken alone — will buy no more than a 15 percent to 20 percent reduction in daily vehicle traffic (over a time period during which traffic is expected to grow by 60 percent).

However, a multimodal transportation system would provide alleviation of another sort. Call it continued economic vitality. Or preservation of quality of life. What a regional transit system offers more than anything else is personal mobility.

San Francisco has one of the most congested street networks in the nation. So what? Take BART across the bay. Ride MUNI out to the suburbs. Catch a bus up Market Street. Hang off a streetcar. Ride your bike. Walk! You can drive if you wish, but almost no one has to drive. San Franciscans have many choices. Most commuters in the Front Range have little choice but to drive.

We shouldn’t “subsidize” public transit.

All ground transportation is subsidized.

The percentage subsidy to transit is higher than the subsidy to auto travel. However, the dollar magnitude of highway subsidization is many, many times higher than all other modes combined.

If the property and sales taxes currently being spent each year on roadways were to be replaced with a higher gas tax — so that drivers were paying their own way — that tax would have to be at least 93 cents per gallon. If the costs associated with the externalities (unassigned, unrecovered negative effects like air pollution) resulting from driving were to be recovered through a gas tax along with the public budget subsidy, the tax rate would have to be set at nearly $4 per gallon.

The public financial support of auto travel over the past 50 years has brought about a massive tilting of the economic scales — toward suburban/rural land development and auto-dependent travel patterns. Whether you approve of the outcome or not, it is important to acknowledge that the heavy stream of daily traffic squeezing through our congested highway corridors is not the outcome of a free market system. It is the result of a conscious, concerted, sustained policy of subsidized auto travel.

There are other half-truths in general circulation “The on-street parking in front of my house belongs to me.” (Yes, but it also belongs to the rest of us.) “My parking space at work is free.” (This isn’t even half true.) “Increased telecommuting would alleviate congestion.” (Very little, if any.) “Improved signal timing would alleviate congestion.” (Not much.) “Soon we will have smart highways to alleviate congestion.” (Soon we will have spent billions of dollars on smart highway technology.)

The bottom line is: Traffic is increasing by 2 percent to 4 percent annually, and congestion is almost certainly going to get much worse. The tough policy choices that would enable us to avoid a traffic-choked future are clear enough, but are — as of now — unacceptable to the public and thus unappealing to elected officials.

I guess it’s a little like being a Buffs fan in 1997. It’s a losing season for sure, but at least we can have some fun debating game strategy and sharing a few half-truths.

Jim Charlier is president of Charlier Associates Inc., a Boulder-based transportation planning firm that provides consulting services to local and regional governments throughout the western United States.

I’ve noticed transportation issues (highway congestion, public transit, etc.) are a little like sports (hockey, football, etc.). Everyone is an expert, but no one agrees with anyone else.

One reason we debate transportation so much is we rely too much on a number of common half-truths. These cause trouble precisely because they are at least partially true. Let’s look at some of these half-truths and see how they hold up under scrutiny.

Traffic growth is caused by population growth.

During the 1980s, Colorado’s population grew…

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