TECHBRIEF

Research, Development, and

Technology

Turner-Fairbank Highway

Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

The national Intelligent Transportation Systems (ITS) program includes

the development and application of

advanced systems upon all parts of

the transportation network, including

rural areas. The U.S. DOT has developed the Advanced Rural Transportation Systems (ARTS) program

to meet the needs of travelers in and

through rural areas, as well as the

agencies responsible for the operation and maintenance of the rural

transportation system. The ARTS

program complements the ITS efforts in metropolitan areas and

commerical vehicle operations (CVO)

by studying ways to best implement

technologies that address transportation problems in rural areas.

Advanced Traveler Information

Systems (ATIS)

Development and Testing of a Surveillance and Delay

Advisory System for Rural Areas

and

Evaluation of Satellite Communications System for

Mayday Applications

Publication No. FHWA-RD-99-116

FHWA Contact: Tim Penney, HRDS, (703) 285-2174

In early 1993, the Federal Highway Administration (FHWA) initiated a

comprehensive study of rural applications of Advanced Traveler Information Systems (ATIS). The study objectives were to guide Federal programs with respect to Intelligent Transportation Systems (ITS) technologies in rural and small urban areas and to provide guidelines for ATIS

implementation by State and local governments to meet rural travelers’ needs. A series of concepts have subsequently been developed in

response to the needs of travelers in rural and small urban areas. Two

concepts are highlighted in this TechBrief — Traveler Services Information and Emergency Response.

DEVELOPMENT AND TESTING OF A SURVEILLANCE AND

DELAY ADVISORY SYSTEM FOR RURAL AREAS

Background

Travelers in rural areas are often faced with traffic congestion and excessive delays when traveling through construction areas or at approaches to rural attractions. Due to a lack of alternate routes, the impact of traffic congestion in rural areas can be more severe than in urban areas. This can create costly and frustrating delays, especially when

travelers have no idea of the extent of the delay until they are part of

the resulting congested flow. Therefore, travelers are interested in traveltime information that reflects current conditions through these congested areas. Travel-time information is of value to traffic managers as

well, as it enables them to manage the traffic through these areas. Development and initial testing of a Surveillance and Delay Advisory System (SDAS) were conducted as part of the “Rural Applications of Advanced Traveler Information Systems (ATIS)” study sponsored by FHWA.
Project Description

The SDAS was developed to enhance data collection capabilities

for travel-time monitoring in congested rural areas. The SDAS employed three different data collection technologies to collect traveltime information — weigh-in-motion (WIM), video-based detection,

and spot speed measurement. The

system gathered data from a test

zone; computed travel times and

delays through the zone; and transmitted delay messages, if any significant delay occurred, to motorists traveling through the zone. The

test was conducted on a section of

State Route (SR) 55 in rural southern New Jersey. This section of SR

55 experiences traffic congestion

during weekends in the summer

due to heavy travel to the New Jersey beaches.

System Capabilities

Three methods were used to collect

data for the SDAS: Two methods—

WIM and video-based detection—

directly measured travel times

through the area, while a third

method—radar detectors—involved

converting spot speed measurements into travel times. Data from

each method were used to independently compute the delay time

through the desired area. The communications for the SDAS can

be broken down into two types: (1)

from the data collection device to

the central processor and (2) from

the central processor to the dissemination interface. The data processing involved receiving data, performing delay-time computation,

and formulating and delivering the

appropriate messages to the traveler interfaces. Changeable message signs (CMS) and highway advisory radio (HAR) were used to disseminate information to travelers.

Project Goals/Objectives

The purpose of this work was to

develop a travel-time monitoring

system using various technologies

and to evaluate the system for its

application in a rural setting. The

system was developed to enhance

data collection capabilities for

travel-time monitoring in rural

areas. The initial testing of the

SDAS helped to achieve the following goals:

• The accuracy of spot speed

conversion to travel times using

three different algorithms was

determined under a limited

range of operating speeds.

• Travel times computed from

spot mean speed versus space

mean speed were compared

under a limited range of operating speeds.

• It was determined that when

certain WIM conditions are met,

automatic vehicle identification

(AVI) applications are effective in

travel-time monitoring.

• It was determined that under

free-flow speed operating

conditions, less than 2 percent

of AVI matches are needed to

compute reliable travel times.

• Although the system was

designed to be capable of

relaying delay information to

travelers, this capability was not

tested due to lack of extensive

delay during the test period.

• The SDAS was cost-effectively

prototyped and tested in a rural

setting.

Future Activities

The tests conducted under this

project provided valuable insight

regarding applications of various

technologies for travel-time monitoring in rural areas; however, additional work is required prior to

actual implementation of such systems. The bulk of this work consists

of validating travel-time calculations under a range of operating

speeds. With respect to WIM technologies, the following work is recommended:

• Calibrate WIM sensors to peak

accuracy.

• Collect a set of data during

actual delay conditions and

correlate it with data collected

by other manual or video AVI

methods possibly using specific

test vehicles.

• Axle spacing, axle weight, and

time window tolerance should

be adjusted to optimize matching performance on the test

data.

• Test runs should be made with

specific vehicles to evaluate

matching performance when the

vehicle speed differs from one

site to the next and to find out

the lowest speed at which

matches can be reliably made.

• The data for matched two-axle

vehicles should be analyzed to

see if valid matches are being

made for long wheel-base

vehicles or if all two-axle vehicles should simply be ignored.
The following work with spot speed

detectors is recommended:

• Different manufacturers of radar

detectors should be evaluated

(given the difficulties experienced doing this test).

• More testing of the spot speed

technology is needed. Spacing

between detectors should be

1.61 km (1 mi) or less for reasonable travel-time computations.

• Alternate sources of power

should be explored to replace

gel cell batteries. A standard

power drop would be ideal;

however, in many rural areas it

is not available.

• If daisy-chain communications

are not desirable, additional

modes of communication

should be explored, possibly

spread-spectrum radio or

telephone lines, if available.

Finally, for video-based travel-time

computations, recommendations

for future activities are as follows:

• It would be desirable to repeat

the testing when seasonal traffic

creates congestion. Such a test

would provide support to the

claims that the use of video in

congested traffic might be useful

in travel-time computations.

• Enhancements to the matching

algorithm include improved

robustness over varying lighting

and weather conditions. In

addition, remote camera control

capabilities are planned that

would enhance low-light operations.

The technology shows promise for

rural areas that experience delays.

However, additional testing is recommended.

The project partners are: SAIC,

TransCore, New Jersey DOT, International Road Dynamics (IRD), and

Nestor Inc.

EVALUATION OF SATELLITE

COMMUNICATIONS SYSTEM

FOR MAYDAY APPLICATIONS

Background

Approximately 60 percent of all fatal accidents occur in rural areas.

Travel speeds are higher and travel

density (the ratio of vehicle-miles

to highway-miles) is lower in rural

areas than in urban and suburban

areas. Other factors influencing the

disproportionate share of rural fatalities include the additional time

required to notify emergency service providers and the length of

time for these service providers to

respond to the incidents. In fact,

data from the Fatal Accident Reporting System (FARS) show that

it takes almost twice as long to be

notified of rural incidents involving

fatalities compared to urban incidents (8.38 min versus 4.35 min).

The significant human and monetary losses associated with these

accidents could be reduced

through an effective “Mayday” system capable of responding rapidly

to motor vehicle accidents and

other traffic incidents. The reduction in response time achieved by

such a system could significantly

improve victim survival rates and

decrease the severity of injuries by

providing victims with more timely

medical attention. Recognizing that

wireless communications (e.g., cellular telephone) in rural areas are

not expected to provide ubiquitous

coverage, this project focused on

studying satellite communications

systems that could provide full coverage in all rural areas, as well as

urban areas, and could be integrated into a Mayday system.

Project Description

The project was specifically tasked

to evaluate satellite communications systems that may be applied

to national/regional Mayday systems. The work included the research into and testing of current

and near-future geosynchronous

earth orbit (GEO) and low earth orbit (LEO) satellite communications

systems. Both voice and data twoway communications were considered. The research effort included

the following: availability of satellite communications technology,

transmission time for relaying a

message from a remote location to

a potential response center, estimated initial capital cost to the user,

and estimated recurring cost to the

user.

Evaluation Approach

Test plans were developed for

evaluating systems and equipment

tested based on defined functional

and performance requirements.

Preliminary study and testing of

accuracy of vehicle position by

communications satellites were

also conducted. The delay time for

transmission, time to transmit, time

to relay transmission from satellite,

and transmission/data capacity

was determined. In addition, the

performance was evaluated in
mountainous and level terrain, under a range of geographic locations

and high foliage density.

Summary and Conclusions

Satellite communications improvement over the next few years is a

key element in the future viability

of rural Mayday systems. Other

findings determined in the study

included:

• As measured in this study,

satellite communications times

are short enough to support an

improvement in notification

times to emergency responders.

• Satellite voice and data modes,

or a combination of the two, can

play a future role in rural Mayday systems. The preferred

mode of operation will be driven

by operational requirements and

may change from region to

region. Viable satellite systems

to support these modes are

available and will be even more

so in the future. Mayday processing architectures are somewhat driven by data/voice

considerations. Operational

requirements that lead to a data

or voice decision should be

independent of communications

carriers.

• The evolving Mayday architecture must be flexible enough to

accommodate improvements

and changes in the wireless

product offerings scheduled for

introduction into the 21st century. The wireless industry is

one of the most dynamic in the

high-tech business sector and

no architecture can afford to be

dependent on a particular mode

of communications. Overall,

Mayday functionality must look

at communications as a transparent subsystem, with no

significant difference between

satellite and terrestrial systems.

• Satellite communications

offerings are a private venture,

and it is logical to conclude that

Issued April 1999 Publication No. FHWA-RD-99-116

services related to this mode of

communications will be largely

driven by the private sector.

Therefore, it is even more of an

imperative to develop a national

Mayday architecture that encompasses not only the private

sector, but the specialized needs

of the public safety community

as well.

The need for wireless communications everywhere is essential, especially in rural areas. However,

recognizing that cellular coverage

still has weaknesses, satellite communications show promise in rural areas. Additional testing is recommended.

For more information

The project partners are SAIC and

TransCore. For more information

on either of these studies, please

contact Tim Penney, Office of

Safety Research and Development,

HRDS, (703) 285-2174.