• They use outdated fuel and emission models that ignore newer engine technologies. This exaggerates fuel savings and emission reductions.
• They ignore the impact of generated travel (additional peak-period trips) and induced travel (absolute increases in total vehicle travel) caused by roadway expansion.
Comparing Congestion Reduction Strategies
This section uses a comprehensive framework to evaluate various congestion reduction strategies.
Roadway Capacity Expansion
Roadway expansion includes traffic signal synchronisation, intersection flyovers, grade separation, adding new lanes and building entirely new roadways. Such projects are costly. Urban highway capacity expansion projects often cost $10-20 million per lane-mile. This represents an annualised cost of $300,000-700,000 per lane-mile, or 15-75¢ per additional vehicle-mile of travel. Road tolls of this magnitude tend to significantly reduce travel demand (Spears, Boarnet and Handy 2010). As a result, few roadway expansion projects can be financed primarily through user fees.
Improving Alternative Modes
Alternative modes include walking, cycling, ridesharing, public transit and telework. High quality public transit (relatively convenient, fast and comfortable) tends to be particularly effective at reducing congestion by attracting peak-period travellers who would otherwise drive.
Several studies indicate that per capita congestion costs tend to be lower in cities with high quality, grade-separated public transit (Kim, Park and Sang 2008). Aftabuzzaman, Currie and Sarvi (2010) concluded that in Australian cities, high quality public transit provides $0.044 to $1.51 worth of congestion cost reduction per transit-vehicle km of travel, with higher values where traffic congestion is particularly intense. Similar patterns are found in developing countries, as summarised in the photograph on the left, which shows that Indian cities with rail transit systems tend to have less roadway congestion.
Transport Pricing Reforms
Various transport pricing reforms are advocated to achieve various planning objectives. Most help reduce traffic congestion.
The table ‘Congestion Reduction Strategies’ summarises the four congestion reduction strategies. Roadway expansion can provide short-term congestion reductions, is commonly considered in the planning process, and provides minimal co-benefits. Improvements to alternative modes, particularly grade-separated transit, can provide significant congestion reductions and numerous co-benefits. Pricing reforms can provide large congestion reductions and numerous co-benefits.
Optimal Congestion Solutions
This analysis indicates that optimal congestion reduction involves the following steps:
1. Apply pricing reforms including road tolls, user-paid parking, fuel price increases, and distance-based insurance and vehicle registration fees to the degree justified by comprehensive evaluation, including consideration of road and parking facility cost recovery, traffic safety, energy conservation and emission reductions, etc.
2. Improve alternative modes, particularly grade-separated HOV facilities and public transit services to the degree justified by comprehensive evaluation, including consideration of road and parking facility cost savings, mobility for non-drivers, traffic safety, energy conservation and emission reductions, etc.
3. Apply congestion pricing (variable tolls or fees that are higher during congested periods), with prices set to reduce traffic volumes to optimal levels, which is typically LOS D. Ideally, this would involve a comprehensive system that allows congestion pricing at any location and time, but if that is infeasible apply special tolls where congestion problems are severe, such as major urban highways and commercial centers.
4. Expand roadway capacity where congestion pricing revenues can finance their full costs. For example, if a particular roadway expansion would have annualised costs of $5 million, implement it if toll on peak-period travellers will generate that much revenue. Tolls on off-peak travellers can be used to finance other roadway costs (maintenance and operations, and safety improvements) but not capacity expansion.
Implications for Developing Countries
This analysis has important implications for developing countries. Over-estimating congestion costs and roadway expansion benefits creates excessively automobile-oriented transport systems which increases various economic, social and environmental problems. Developing countries can avoid future problems by applying more comprehensive congestion costing analysis.