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WHY REDUCE CONGESTION?

• Impacts to individual: lost time
• Impact to society: “traffic congestion is undesirable because it misallocates scarce resources and causes economic inefficiency
• Government response to public concern: allocation more resources than is socially optimal to building roads and subsidizing public transportation; congestion also causes land use inefficiencies (sprawl) because firms and workers try to reduce travel times by decentralizing jobs and housing
• Impacts are in part because drivers and businesses do not pay true social costs—commuters do not have to pay the costs of added congestion they impose when traveling during peak hours

REGIONAL NATURE OF TRAFFIC CONGESTION

• The regional nature of the road network: traffic they carry is heavily influenced by conditions outside the boundary of each community; most communities fail to look outside their boundaries in responding to traffic—in part because they have no legal authority

ISSUES

• Whether peak hour traffic congestion can be effectively reduced without a significant degree of regional planning and coordination of the factors that affect travel patterns
• Required degree of regional control varies greatly among anti congestion policies
• Polices are most effective when voluntary cooperation occurs between various local governments
• However, these governments will never voluntarily agree on how to make hard choices regarding congestion policies
• Each will seek to maximize its own residents’ benefits and minimize their bearing any social costs
• Therefore, decisions necessary to reduce congestion effectively can only be made by one ore more regional bodies with true authority and power not only over traffic flows, but also highway and transit planning and construction, location of land uses, and density of development
• Many questions arise about regional governance

WHAT FACTORS INFLUENCE URBAN TRAVELER DECISIONS?  

• Travelers and businesses use a number of factors to evaluate their trip and the transport system. This report evaluates some but not all of these. Here are some questions that people ask about travel to give the reader an idea of how broad the topic is and to place the report in the proper context

• Can I get there?— This is often the first question asked by those without ready access to a personal vehicle. It may also include questions about parking near the destination.

• How long is the trip?— Sometimes this is related to distance, but usually it is a time measure. It includes, for example, time spent waiting for transit service or walking from a parking place to a destination.

• What are my travel mode options?— How many ways are there to make the trip that satisfy my needs?

• What route do I take?— What roads, paths or transit routes do I use? And do these change depending on when I’m traveling?

• When do I leave?— This relates to trip time and to the variability in trip time for the mode and route chosen. Travel time variability is particularly important to freight shippers involved in just-in-time manufacturing.

• Will I be comfortable and safe?— Many times the uncertainty in these two factors will be an incentive to take a known mode/route rather than experiment.

• Is the trip convenient?— This relates to a mix of route, mode and time choices and frequently explains why driving alone is chosen even when it costs more.

• How much will it cost?— Frequently users seem to view their time, vehicle operating costs and out-of-pocket expenses (e.g., tolls, fares) differently even though all can be expressed in monetary terms.

• Do I need to make this trip?— In the context of urban areas, this is often thought of as a question that leads to an “electronic trip” to telecommute or “teleshop.” It is also a significant question for those without easily available travel options and in areas with climatic extremes.

CAUSES OF RECENT INCREASES IN CONGESTION

Immediate causes

1. Rapid population and job growth—congestion most pronounced in fast growth areas
2. More intensive use of automobiles—more people are driving more cars more miles—contributes more than population exact in very fast growing areas
3. Failure to build new roads—between 81 and 89, road miles increased 0.6% while the number of vehicles grew 24% and VMT 34%
4. Failure to make drivers bear the full costs they generate

Long-term causes

1. Concentration of work trips in time (am/pm commute)—work days start and end at the same time so employees can interact, the resulting efficiency is thought to outweigh the costs of delay caused by trip concentration –all of the firm costs are externalized onto the workers
2. Desire to choose where to live and work—many commuters willing to travel long distances so they can live and work where they choose—key reasons: good schools, like their house; like their neighbors; jobs too far from jobs of other family members
3. Desire for low-density neighborhoods—goal of many Americans: sfr with private open space; result –spread housing out over much larger area than hdr; residential densities are affected by the relative movement of population from metro areas of the NE and Midwest to ones in the south and west built during the auto era—of 182 cities w/more than 100000 people in 1986, the 22 in NE had average density more than 3x that of 39 in Midwest and more than 6x the average of cities in the other regions
4. Preference for low-density work places—many suburbs require offices, retail facilities, manufacturing, etc to be housed in low-rise structures with low FARs—both residents and tenants like adjacent free ground-level parking and attractive landscaping; communications technology has facilitated low density employment; suburban office space often cheaper than CBD; more new jobs being created in suburbs than CBD; this combined with ldr reduces the feasibility of commuting by mass transit; moving low density emp and housing to suburbs can decrease commute time, but doesn’t necessarily imply shorter commute distances
5. Desire to travel in private vehicles—most Americans prefer to travel in private vehicles, often alone because: convenience, comfort, privacy, and speed superior to public transit; it is extremely difficult to increase the benefits of alternative modes; so most likely solution is to decrease benefits of driving alone, mainly by costs

 Summary: key causes of congestion rooted in long-established beliefs and behavior patterns

 STRATEGIES FOR REDUCING CONGESTION

• Supply side—more roads more capacity
• demand side—encourage ride sharing, etc

Market based approach

• assign monetary value to different travel behaviors and then rely on commuters to choose among them; advantage: more choice, more flexible, requires less law enforcement; complaint: stress on low-income households, called regressive and inequitable

Regulate

• mandate certain behaviors and prohibit others

Most strategies will rely on a combination of the two

THREE PRINCIPLES OF TRAFFIC ANALYSIS

1.      Triple convergence—drivers converge on “best” routes (quickest, shorter, less encumbered by obstacles); example—new expressway

a.      Spatial convergence: Many drivers who formerly used alternate routes during peak hours switch to the expressway

b.      Time convergence: many drivers that formerly traveled before or after peak hours start traveling during those hours

c.       Modal convergence: some commuters who formerly used public transportation or alternative modes switch to driving because it has become faster

Result: more and more drivers use expressway during peak hours, causing traffic volumes to keep rising until vehicles are once more moving at a crawl; may increase burden on alternative routes

But, highway improvements that expand hourly road capacity clearly produce social benefits—the total number of vehicles moving towards destinations will be greater than before, peak hour congestion may become shorter if total number of vehicles does not increase; traffic will move faster before and after peaks; except for decline in public transit use the region will be better off

Converse of triple convergence—any factors that serve to increase peak-hour congestion on limited-access roads will cause users of those roads to (1) shift to the same road in non-peak periods, (2) alternative routes during peak periods, or (3) transit. This has important implications: residents in fast-growing areas want to avoid spillover traffic onto residential streets—to many residents such spillover is as great a concern as congestion

It is widely assumed that high levels of peak-hour congestion will support transit patronage—which is why they are making large investments in transit. That is why they make large investments in transit; however, there is little evidence that it has any significant impact on peak-hour congestion

2.      Duel Swamping by Growth—If 5% capacity is added, it will be offset in a short period by population growth and growth in VMT. Remedy that cuts peak-hour travel (other than road widening) can easily be consumed by year 3 if the number of vehicles in use is growing 2.5% annually.

In many cases part of vicious cycle—improvements are made in capacity which create incentives to (1) increase automobile ownership and use, and (2) change the location and form of both residential land non-residential development (low density/dispersed)

Growth in any major metropolitan area is mainly the result of whatever forces are creating jobs in the long run, not highways. Highways determine where growth will occur, not how much.

Traffic congestion caused by rapid growth is very difficult to relieve if growth has been caused by other than good transportation facilities

3.      The imperviousness of growth to public policies—no growth policies impractical. Extremely difficult to stop growth if factors support employment growth—particularly in metro areas. If one suburb adopts policies to slow or limit growth, it simply diverts growth to another community.

Antigrowth policies difficult to sustain because of the economic benefits of growth. As incomes rise, purchasing power increases and more money is spent in local stores and businesses. With more commercial/industrial development, tax revenues increase lessening the burden on residents

SUMMARY

            Public policies should strive to:

1.      Reduce the duration of maximum congestion appreciably

2.      reduce the average length of time required for commuting

3.      increase the average commuting speed

4.      increase the proportion of commuters traveling during the period of maximum convenience

5.      reduce the intensity of commuter frustration

SUPPLY SIDE REMEDIES

• Building more roads—not effective because of triple convergence; duel swamping

• Making transportation systems more efficient

1. programmed repairs and improvements aimed at keeping highways in good shape
2. coordinated timing of traffic signals along arterial streets – can increase speeds by 12 – 25 percent
3. use of multiple repair vehicles to deal with traffic
4. television monitoring systems to identify accidents quickly
5. upgrade normal city streets to limited access
6. two way to one way streets
7. ramp signals
8. electronic information signs
9. street parking patterns changed to make more room for traffic

• Using more HOV lanes

• Building more public transit capacity

Transit use pretty low overall (~5%)

People most likely to use transit: (1) have no auto, (2) live in central city and work in CBD, and (3) live in a densely settled community

Conclusion: large increases in transit use will not greatly relieve suburban traffic congestion—a doubling of transit use would result in a 3-5% decrease in suburban auto commuting

DEMAND SIDE REMEDIES THAT DO NOT CHANGE HOUSING OR JOB LOCATIONS

Peak hour road pricing—toll more effective than time delay ration approach

             Equity issues: (1) not fair to lower income households (2) looks like another tax

            Some argue that the benefits from use of road funds from peak hour pricing and faster movements would make everyone better off

             Efficiency issues: not much of an issue now—technology exists to implement

             Impacts: divert trips to non-priced routes , transient vehicles and traffic diverted to non-peak hours, through traffic

POTENTIAL ALTERNATIVES

Given the above, what alternatives exist to congestion? Four potential  scenarios that are reviewed include:

¨ Sit in traffic— This item will focus on the size of the congestion problem in 1997. The gallons of fuel and hours of time wasted because of congestion are discussed. Also, a price tag is placed on the wasted fuel and hours to show the magnitude of the congestion problem in terms of dollars.

¨ Build roads— How much roadway do we need to build to stay even in the battle with traffic congestion? This item shows how many additional lane-miles of roadway would need to be constructed in each urban area in order to keep up with the growing traffic demand.

¨ Range of improvements— Many different improvements have been utilized in an effort to deal with traffic congestion. These improvements include such techniques as increased transit service, freeway incident management, HOV lanes, travel demand management and many others. The HOV lane system in Houston will be used as a case study to show the effect that these lanes have on mobility levels in Houston at both the corridor level and area wide.

¨ Changing occupancy— Similar to the discussion about how much new roadway would need to be added to avoid congestion growth, this item looks at the average vehicle occupancy rates to accommodate all of the new travel demand in an area.

 OTHER RESOURCES

• Oregon Department of Transportation Planning Page

• Texas Transportation Institute

• Transportation Demand Management Page

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This page maintained by Bob Parker
January 31, 2002