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How bad will traffic congestion be in 2030? How much construction and how many new lane miles will each state and major city need to add over the next 25 years to prevent severe congestion? And how much will it all cost? The Reason Foundation study Building Roads to Reduce Traffic Congestion in America's Cities: How Much and at What Cost? and its addendum, A Detailed State-by-State Analysis of Future Congestion and Capacity Needs, provide in-depth answers to these questions. An interactive map ranking the states by congestion and costs to reduce traffic is here and a map of the most congested cities is here.

Idaho

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To significantly reduce today's severe congestion and prepare for growth expected by 2030, Idaho needs just over 275 new lane-miles at a total cost of $372 million, in today's dollars. That's a cost of approximately $22 per resident each year. Idaho ranks 39th out of 50 states and the District of Columbia in terms of most lane-miles needed and 42nd in the total costs of those improvements. If the state made these improvements, it would save almost 2.6 million hours per year that are now wasted in traffic jams.

As Table 18 suggests, Idaho really does not have a significant traffic congestion problem, although there are likely to be specific sites in the state where traffic does have some major adverse impacts. The five cities in Idaho with populations over 50,000 (Boise City, Nampa, Coeur d'Alene, Pocatello, and Idaho Falls) all have Travel Time Indices (TTIs) in the 1.04�1.05 range. This means that driving times during peak traffic hours are 4�5 percent longer than during off-peak times. While these TTIs do not reach the 1.18 level that this study identifies as severe congestion, the relative increase in delay projected over the next 25 years for each of these cities is 100�120 percent, which will be sharply noticed by local commuters. (The 'delay' in the travel time is that portion of the TTI over 1.0.) To put things into perspective, TTIs of around 1.08 reflect current traffic in larger cities such as Cleveland, Richmond-Petersburg, and Spokane. Idaho could solve this problem by adding 275 new lane-miles by 2030 at an estimated cost of $372 million in today's dollars.

This investment would save an estimated 2.6 million hours per year that are now lost sitting in traffic, at a yearly cost of $5.76 per delay-hour saved. This does not account for the additional benefits not quantified in this study, including: lower fuel use, reduced accident rates and vehicle operating costs, lower shipping costs and truck travel time reductions, greater freight reliability, and a number of benefits associated with greater community accessibility, including an expanded labor pool for employers and new job choices for workers.

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This information is excerpted from A Detailed State-by-State Analysis of Future Congestion and Capacity Needs and Building Roads to Reduce Traffic Congestion in America's Cities: How Much and at What Cost?

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