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06.09

Intelligent Highways Aid Capacity and Safety

By George McClure

Every year in the United States, vehicle accidents result in more than 42,000 fatalities. This statistic has remained about constant over the past decade, even though the vehicle miles traveled has grown by 21 percent, to more than three trillion in 2006. Lives saved by seat belts have grown by 44 percent over the decade; for air bags the life-saving is a more dramatic increase of 250 percent. [1]

Vehicle miles traveled (VMT) — the measurement of the total miles traveled by all vehicles in a specified area during a specified time — increased by 76 percent between 1980 and 1999, while total highway miles grew by only 1.5 percent. [2] There are 4 million miles of public roads in the United States. [3] Over 10 percent of the gross Domestic Product is transportation- related. For the average household, 19 percent of the budget goes for transportation — as much as for food and health care combined — and is second only to spending on housing.

Figure 1. More than ten percent of GDP is related to transportation

Source: U.S. Department of Transportation, Bureau of
Transportation Statistics, Pocket Guide to Transportation 2009
 

The Interstate Highway System accounts for only 1 percent of all highway mileage, but carries 25 percent of the total vehicle miles of travel. The cost of expanding this system underscores the desirability of safely increasing the number of vehicles carried in existing lanes. [4]

The National Research Council of the National Academies, through the Transportation Research Board (TRB), appointed a committee to address some of the most pressing concerns about highway transportation. The second Strategic Highway Research Program (SHRP 2) reported on those concerns. [5] Chief among them are congestion, safety, renewal of infrastructure, and provision for growth. In 2005, congestion cost travelers in 437 urban areas over 4.2 billion hours and nearly $80 billion. It resulted in the waste of about 3 billion gallons of fuel. Population growth will exacerbate the problem. The U.S. population is expected to grow by 24 percent by 2030. There could be a need for 5,700 new lane-miles of Interstate highways each year for the next 30 years. By 2030, the number of vehicle miles traveled will increase by 60 percent, with trucks increasing by 75 percent and truckloads predicted to increase by 80 percent by 2035. SHRP 2 needs sustained funding, estimated at $400 million for the first six years of the implementation program.

Role for Intelligent Transportation Systems

Intelligent Transportation Systems (ITS) include a variety of initiatives that can improve highway safety and reduce congestion when fully implemented. The Federal Highway Administration is pursuing the Vehicle Infrastructure Integration (VII) initiative to facilitate vehicle-to-vehicle and vehicle-to-infrastructure communications for the exchange of critical information.

The ITS Radio Service in the 5.9 GHz band was established in 2003 for Dedicated Short Range Communications (DSRC). Its use will permit a vehicle applying emergency braking to automatically notify a following vehicle. It can also notify of approaching emergency vehicles, notify of roadway conditions, and provide data for in-vehicle displays. The VII system will include a DSRC radio and a Global Positioning System (GPS) receiver inside the vehicle and at the roadside. The roadside equipment will also include a network interface for transmitting data.

For nationwide deployment of VII, there would have to be between 100,000 and 400,000 roadside devices installed and maintained by the U.S. Department of Transportation (USDOT). A nationwide Internet Protocol network will collect and distribute data. Advanced traffic management systems (ATMS) can collect data from vehicles to provide overall system status at traffic management centers.

Funding for Research and Intelligent Transportation System (ITS)

The Federal Highway Administration (FHWA) conducts and manages a comprehensive research, development, and technology program. For FY 2009, $429.8 million is estimated for research. FHWA will continue to work on identifying ways to reduce the number of injuries and fatalities on our Nation’s roadways by demonstrating the application of innovative technologies in highway safety, deploying and evaluating safety technologies and innovations at the State and local levels, and assuring the deployment of best practices in training, management, design, and planning. For FY 2009, $110 million is estimated for the ITS program, now managed by the Research and Innovative Technologies Administration of DOT (RITA), to continue work on ten major initiatives and supporting technology transfer activities. Key among the initiatives is Vehicle Infrastructure Integration (VII), now renamed IntelliDrive, which continues development of enabling wireless platform to connect vehicles-to-vehicles and vehicle-to-infrastructure, along with safety and mobility applications. The ITS program also continues work in the deployment and integration of technology components to support congestion initiatives. [6]

Highway Capacity Improvement with ITS

Simulations have been used to estimate the improvement in lane capacity if vehicles traveled with very short vehicle spacings using automated control techniques. The biggest improvement would be the elimination of driver reaction time (1.2 to 1.7 seconds), with automatic control. But there may be a communication delay introduced (60 msec has been assumed). If a vehicle spacing of 50 meters can be attained, at 110 Km/h (70 mph) it is possible to achieve 2000 passenger cars per hour per lane. With even tighter spacing and a decrease in the hardware time delay, using a platoon system, the computer model suggests that capacity can be raised to 3 to 3.5 times that currently achievable. [7]

Fuel Economy and Safety

With the newly proposed fleet wide fuel efficiency of 39 miles per gallon for passenger cars by 2016, from 27.5 miles per gallon today, there will be more incentive to reduce vehicle weight. In collisions, lighter vehicles may suffer more damage than heavier vehicles. The National Research Council estimated that in 1993 there were between 1,300 and 2,600 motor vehicle crash deaths that would not have occurred if cars were as heavy as they were in 1976. Nearly half of all car crashes are one- vehicle crashes, involving a tree or other stationary object. [8] Vehicle avoidance becomes even more important with lighter weight cars. The proposed $4500 payment for older cars removed from the roads could encourage upgrading to new cars that may be equipped for intelligent highway operation.

Other Improvements Possible

In 2004, urban areas experienced an average of 6.6 hours per day where roads were congested, compared to free-flow conditions. The urban travel time index stood at 1.38, meaning that travel times were 38 percent longer than for free flow conditions. For the average peak period commuter, this meant that an annual delay of 45.7 hours was incurred — time spent on the road that could be better spent otherwise had there not been congestion. [9]

Intelligent transportation systems can help solve the capacity problem without the expense of building all the additional highway lanes required without ITS. The cost of electronics required in vehicles will come down with the millions of units required; the experience with GPS and cell phones is instructive.

Some safety improvement is possible with sensor-controlled autonomous braking, even without the fixed infrastructure. [10]

References

1. National Transportation Statistics 2008, www.bts.gov/publications/national_transportation_statistics/2008/index.html

2. "Closing the Safety Loop: Linking Smart Vehicles with Intelligent Highways," Technology Today, Spring 2007 http://www.swri.org/3pubs/ttoday/Spring07/PDFs/SafetyLoop.pdf

3. Transportation of the United States http://nationalatlas.gov/transportation.html

4. National Surface Transportation Policy and Revenue Commission, Final Report, Transportation for Tomorrow, December 2007
   http://transportationfortomorrow.org/final_report/

5. Transportation Research Board Special Report 296, Implementing the Results of the Second Strategic Highway Research Program: Saving Lives, Reducing Congestion, Improving Quality of Life, http://onlinepubs.trb.org/onlinepubs/trnews/trnews261SHRP2.pdf .This is a summary. Full report (186 pp.) available online.

6. USDOT 2009 Budget in Brief http://www.dot.gov/bib2009/htm/FHA.html

7. Brake Dynamics Effect on AHS Lane Capacity http://vehicle.me.berkeley.edu/Publications/AHS/dbmac_saeftt95.pdf

8. "Light Cars Are Dangerous Cars," Wall Street Journal, 22 May 2009
   http://online.wsj.com/article/SB124294901851445311.html

9. Commission Briefing Paper 2A-01, 2006 C&P Findings: Highway Condition and Performance http://transportationfortomorrow.org/final_report/pdf/
   volume_3/technical_issue_papers/paper2a_01.pdf

10. Z. Wu, Y. Liu, G. Pan, "A Smart Car Control Model for Braking Comfort Based on Car Following," IEEE Transactions on Intelligent Transportation Systems, Vol. 10, No. 1, March 2009, pp. 42-45.

George McClure is Technology Policy editor for IEEE-USA Today’s Engineer and the IEEE Vehicular Technology Society's representative to IEEE-USA's Committee on Transportation and Aerospace policy. Comments on this article may be submitted to todaysengineer@ieee.org.