Study Challenges Theory that New Roads Encourage People to Drive More

Written by Posted On Wednesday, 10 January 2007 16:00

A new study, funded by the Canadian Construction Association, challenges the popular theory that building new roads encourages more people to drive and increases the amount of traffic in a community. The study says that if the goal is to reduce greenhouse gas emissions, "restricting the physical capacity of the road network is not an effective approach for Canada."

"Build It and Will They Drive? Modelling Light-Duty Vehicle Travel Demand" was produced by Greg Hoover and Michael Burt for the Conference Board of Canada. The study developed an economic model to look at travel demand on Canadian roads and "is the only Canadian model to incorporate social-economic variables in the exercise," say the authors. These factors include population density, income, the cost of vehicles and fuel, demographics and "vehicle-specific" data, the study says.

"Many transportation experts argue that the only way to achieve a sustainable transportation network is to increase the density of new and existing communities," write Hoover and Burt. "Expanding the existing road network capacity is not an option, they assert, because it only perpetuates existing greenhouse gas emission trends and, at best, is a short-run solution to transportation network congestion. Increases in highway capacity, they contend, lead directly to increased road network demand."

The study found that there is a "weak" relationship between road improvements and "induced travel," which is defined as the increment of new traffic that would not have occurred without capacity improvements. It says for every one per cent increase in lane-kilometres, there is a 0.49 increase in kilometers traveled by light trucks, and a 0.26 increase in car traffic. "Thus, if road building continues at a pace that matches the rate of population growth, no induced travel is to be expected," says the report. "It is only when construction surpasses the rate of population growth that an argument, albeit weak, for an induced travel effect is apparent."

The study says that "simply reducing the physical capacity of the road and highway network is not an effective policy for mitigating greenhouse gas emissions … . Instead, socio-economic policies designed to influence individual behaviour (such as adjusting fuel taxes or land-use policy designed to increase the density of cities) are much stronger tools for mitigating travel demand."

The Conference Board study says that the single largest determinant of travel demand is population density. However, as population density increases, the share of travel demand per capita decreases, since residents are closer to the places where they work and the services they require.

Wealth plays a role in the second-largest determent of travel demand, which is the number of vehicles per person of driving age. "Our analysis demonstrates that in the case of cars, for every one per cent increase in the number of vehicles per person of driving age in Canada, there is a corresponding 1.01 per cent increase in per capita travel demand," says the report. The report also found that real per capita disposable income adds to the number of cars on the road. "For every one per cent increase in real per capita disposable income, per capital travel demand in Canada increases by approximately 0.7 per cent," say the authors.

The price of gasoline relative to the price of local transit also plays a role.

A 2005 study by Transport Canada concluded that the costs of congestion in the country’s major cities cost between $2.3 billion and $3.7 billion in lost productivity. The Conference Board study suggests that the best way to reduce travel demand is by hitting consumers in the pocketbook.

"Canada is a market-based economy; therefore, directly limiting the number of cars per capita or actively dampening personal disposable income growth are non-starters," says the report. "Instead policy-makers would need to indirectly influence consumer behaviour -- that is, alter how people make their spending decisions. Currently, the price of owning and operating a vehicle does not account for all of the socio-economic costs. Adjusting the price to more accurately capture these costs is one potential tool to influence consumer behaviour."

Slapping new taxes on gasoline would make consumers pay attention. Another suggestion is user fees for roads -- one idea would charge higher licence fees that could vary by type of vehicle, type of roads used, and time of day and season. The Conference Board report says road fees would encourage car pooling, shifts in demand to off-peak hours, increased demand for fuel-efficient vehicles and increased demand for urban transit.

However, for this to happen, "societal perceptions with respect to road-pricing must change," say the authors, noting that recent attempts at putting in new toll highways have met with opposition. It some parts of the world, road pricing is proving successful. In London, England, it costs about £8 per day to drive or park in the central part of the city. Since that system came into effect in 2003, congestion is down, public transit has been able to cope with displaced car users, and businesses have not had a significant negative impact, the report says.

Another way that Canada could reduce emissions, says the report, is by having more concrete rather than asphalt roads. "Though more relevant to tractor-trailer units that personal vehicles, rigid (concrete) pavements distribute the mass of the vehicle over a broader area than flexible (asphalt) pavements, thereby reducing the flexibility in the pavement. This reduces rolling resistance and provides the greatest fuel efficiency of all pavement types."

The report concludes that "a multi-pronged approach" to addressing the issue of travel demand must be developed. "Continuing ‘business as usual’ practices will only serve to exacerbate the costs of congestion on the economy in terms of the value of time lost, and on the environment in terms of total emissions," it says.

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Jim Adair

Jim Adair has been writing about Canadian real estate, home building and renovation issues for more than 40 years. He is the former editor of Canada’s leading trade magazine for real estate professionals, as well as several home building, décor and renovation titles. You can contact him at [email protected]

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