A CASE STUDY

Intelligent Transportation

Systems in Work Zones

Intelligent Transportation

Systems in Work Zones

A CASE STUDY

October 2004

Dynamic Lane Merge System Dynamic Lane Merge System

Reducing Aggressive Driving and Optimizing 

Throughput at Work Zone Merges in Michigan

Reducing Aggressive Driving and Optimizing 

Throughput at Work Zone Merges in Michigan
Notice

The Federal Highway Administration provides high-quality information to

serve Government, industry, and the public in a manner that promotes

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FHWA periodically reviews quality issues and adjusts its programs and

processes to ensure continuous quality improvement.
i

Foreword

Dear Reader,

We have scanned the country and brought together the collective

wisdom and expertise of transportation experts implementing

Intelligent Transportation Systems (ITS) projects across the United States.

This information will prove helpful as you set out to plan, design, and

deploy ITS in your communities.

This document is one in a series of products designed to help you

provide ITS solutions that meet your local and regional transportation

needs. The series contains a variety of formats to communicate with

people at various levels within your organization and among your

community stakeholders:

• Benefits Brochures let experienced community leaders explain 

in their own words how specific ITS technologies have benefited

their areas.

• Cross-Cutting Studies examine various ITS approaches that can be

taken to meet your community’s goals.

• Case Studies provide in-depth coverage of specific approaches

taken in real-life communities across the United States.

• Implementation Guides serve as “how to” manuals to assist your

project staff in the technical details of implementing ITS.

ITS has matured to the point that you are not alone as you move

toward deployment. We have gained experience and are committed

to providing our state and local partners with the knowledge they 

need to lead their communities into the future.

The inside back cover contains details on the documents in this series, 

as well as sources to obtain additional information. We hope you find

these documents useful tools for making important transportation

infrastructure decisions.

Sincerely,

Jeffrey F. Paniati

Associate Administrator for Operations

Acting Program Manager, ITS Joint Program Office

Federal Highway Administration
This case study is one in a series of documents that examines the use of

Intelligent Transportation Systems (ITS) in work zones. More information

on applications of ITS in work zones is available in the companion 

document, Intelligent Transportation Systems in Work Zones – 

A Cross-Cutting Study (Report No. FHWA-OP-02-025, EDL# 13600).

This case study presents information gathered during interviews with

key personnel involved with an Interstate 94 (I-94) reconstruction project

in Detroit, Michigan, as well as information and photos obtained during

a site visit. Interviewees were involved in the deployment of the dynamic

lane merge ITS application on I-94, and were also involved with other

recent deployments of the system. The authors greatly appreciate the

cooperation of the Michigan Department of Transportation, along with

their partners, which made the production of this document possible.

ii

Contents

Preface

PREFACE........................................................................................................ ii

CONTENTS....................................................................................................... ii

PROJECT AND SYSTEM BACKGROUND..................................................... 1-1

SYSTEM DESIGN, SELECTION, AND IMPLEMENTATION.......................... 2-1

SYSTEM DESCRIPTION AND OPERATIONS................................................ 3-1

RESULTS........................................................................................................ 4-1

CONCLUSION............................................................................................... 5-1

LIST OF FIGURES

Figure 1 – DLM Layout on I-94................................................................... 1-2

Figure 2 – Activated ”Do Not Pass” Sign at the I-94 Dynamic

Lane Merge Site.......................................................................... 1-3

Figure 3 – Westbound I-94 Message Board............................................... 3-1

Figure 4 – Back Side of Dynamic Lane Merge Trailer............................... 3-3

Figure 5 – Dynamic Lane Merge System Concept of Operations........... 3-4

LIST OF TABLES

Table 1 – Sensor Settings............................................................................ 3-2
1-1

Project and System Background

The Michigan Department of Transportation (MDOT) rebuilt a large

section of I-94 in Clinton Township (a suburb of Detroit) during the 

2002 and 2003 summer construction seasons. The improvements were

necessary to upgrade roadway geometry and roadside hardware, to

enhance safety and efficiency, and to rehabilitate deteriorating pavement.

This section of I-94 provides access to and within the eastern portion 

of the state. The road parallels the Detroit River, a natural boundary

between the United States and Canada. The work zone on I-94 extended

from Michigan Route 102 (M-102) to Masonic Boulevard, a distance of

about 13 miles, and involved both directions of traffic.

The two-season construction project began on April 1, 2002, and ended

on September 30, 2003. The project involved 13.5 lane-miles of construction,

including bituminous resurfacing, concrete pavement repair, bituminous

freeway and concrete ramp reconstruction, lighting installation, traffic

signal installation (at the end of ramps), water main alteration, and

rehabilitation of 18 bridge structures. The total project cost was $46 million.

For the I-94 project, MDOT deployed a work zone Intelligent Transportation

System (ITS) to help smooth traffic flow and reduce aggressive driving

just prior to the transition into the construction area. MDOT selected a

dynamic lane merge (DLM) system that uses electronics and

communications equipment to monitor traffic flow and, as queuing

increases at approaches to lane closures, to regulate merge movements

and require early merging. The system, developed by International 

Road Dynamics Inc., used microwave radar sensors installed on five DLM

trailers to detect traffic volume, vehicle speed, and detector occupancy.1

The system then used the data to calculate an Activity Index (a function

of volume, speed, and occupancy). When the detected conditions

surpassed the pre-set thresholds established by MDOT, the system would

automatically activate flashing “Do Not Pass” signs. A schematic of the 

I-94 DLM layout, including the five DLM trailers with sensors and flashing

signs, is shown in Figure 1. When traffic conditions no longer warranted

activation, the system remained active for five minutes and then

automatically switched to inactive mode. MDOT spaced the trailers 1,500

feet apart. The closer the trailer was to the merge point, the lower the

Activity Index was for activation. The trailer closest to the merge point

was always on. A close-up of an activated (flashing) “Do Not Pass” sign 

at the I-94 site is shown in Figure 2.

This ITS application was deployed on westbound I-94 in September and

October 2002, and August and September 2003. MDOT decided not to

deploy the system on the eastbound direction because the higher traffic

volumes in that direction would have made the system operate in active

mode almost all of the time. These conditions would have caused the

system to display the same messages most of the time and decreased the

value of using a dynamic ITS technology. MDOT planned to use the

1Detector occupancy is a measure of traffic density.

“The use of ITS on 

the I-94 reconstruction

project has improved

driving conditions in

our area.”

– Robert J. Cannon

Supervisor

Clinton Township

Michigan
1-2

Project and System Background

2Michigan Department of Transportation (2004). Development and Evaluation of an Advanced

Dynamic Lane Merge Traffic Control System for 3 to 2 Lane Transition Areas in Work Zones. 

Figure 1 – DLM Layout on I-942
1-3

Project and System Background

system during the entire 2003 construction season, but experienced

some circuit-related electrical problems that caused deployment delays.

MDOT had used DLM previously on several other sites that included 

two-to-one lane drops, while the I-94 site was the first DLM deployment

in Michigan that involved a three-to-two lane drop.

There were a number of reasons why MDOT used ITS for this major

construction project, including the following:

• MDOT anticipated aggressive driving at the merge point. As queues

build on the approach to work zone lane closures, drivers try to

avoid these queues by using storage space upstream of the closed

lane prior to the merge point. This situation is known as a “late lane

merge” phenomenon, and can create safety and mobility concerns

when drivers attempt to forcefully merge into the through lane at

the last minute.

• MDOT expected speed variability to increase as queues formed in 

the through lanes, and that this could decrease traffic safety and

create a higher risk for crashes.

• MDOT identified a need to provide for smoother flow through 

the merge point at the work zone approach. MDOT believed that

the traffic volumes on westbound I-94 were in a suitable range for

traffic flow to benefit from the DLM system.

The main goals of the ITS system were to:

• Reduce aggressive driving at the merge point

• Maximize available capacity at the merge point just prior to

dropping one lane out of three

• Reduce capacity losses due to increased headways at the work zone taper

• Enhance traveler safety.

Figure 2 – Activated “Do Not Pass” Sign at the I-94 Dynamic Lane Merge Site
2-1

System Design, Selection, and 

Implementation

This section provides information on MDOT’s experience in bringing the

system from the concept stage to fully operational.

• MDOT added specifications for the DLM system components as 

pay items in the prime construction contract after award, as a

modification to the contract.

• The prime construction contractor hired two subcontractors to

design, install, and integrate the system components based on the

specifications that MDOT provided in the contract modification.

• The construction contract called for the leasing, installation and

calibration, and as-needed maintenance of all components of the 

ITS system. 

• MDOT included specifications in the contract for trailers, signs, and

microwave sensors.

• The subcontractor leased all of the system components, as MDOT

specified in the prime construction contract. The period of performance

for the subcontractor was approximately six months during each of

two years, and included installation, testing, and operation time.

• MDOT’s total cost for deployment of the DLM system was $120,000.

• MDOT wrote the specifications for temporary use of the system so

that they could deploy DLM without having to perform equipment

maintenance or store the system after construction was completed.

MDOT continues to use the lease option to benefit from the latest in

rapidly changing technology.

• The subcontractor developed a safety plan for placement of the

DLM system on I-94. The safety plan specified several procedures

that were used, including implementation during off-peak hours to

minimize exposure to traffic.

• Electrical problems with sensor power sources delayed deployment

early in the 2003 construction season. Sensor circuit boards were

ultimately replaced to resolve the problem.

In-House or

Contractor Design

System Selection

and Procurement

Lease Versus

Purchase

System

Implementation
2-2

Testing

Training

• The project special provision for the DLM system called for wireless

communications between sensors. The specification required the

ability to communicate between sensors over a minimum distance of

five miles on an unlicensed transmission band. 

• Following a one-day installation and testing period, the

subcontractor requested approval to turn the system on to traffic.

• Traffic sensor equipment required testing and calibration to ensure

adequate wireless communication between trailers in a closed loop

setting. Each trailer required access to the operational status of the

other trailers in the loop, since they operated as one system.

• The subcontractor performed preliminary testing that focused on

sensor operations and communication among sensors.

• The subcontractors were responsible for all technical aspects of 

the system, including equipment installation, maintenance, and

operation. MDOT did not specify any requirements for formal

training of MDOT employees on these aspects of the system as part

of the contract.

“We are pleased 

that this enforceable

system is being

implemented to help

reduce aggressive

driving and improve

mobility at work

zone merge areas.”

– Robert J. Cannon

Supervisor

Clinton Township

Michigan

System Design, Selection, and Implementation
3-1

System Description and Operations

• The system consisted of five trailers, spaced 1500 feet apart, upstream

of the work zone.

• Each trailer included a flashing “Do Not Pass” sign, communications

equipment, and a power source. All the trailers except the one

furthest from the work zone also contained a Remote Traffic

Microwave Sensor (RTMS). 

• Components relied on solar, rechargeable systems for power.

• The system used wireless radio communication equipment to allow

for communication and data sharing between trailers.

• For the DLM deployment, the only communications requirement 

was to allow the sensors to communicate with each other. 

In addition, the contractor was able to dial up the system from a

remote area to check the status of the system.

• In addition to the DLM system components, MDOT installed two

signs on highway entrance ramps near the work zone to alert

drivers of the no passing zone ahead. MDOT also deployed two

“Form Two Lanes Right” signs approaching the merge area, 

one message board, and six static “Do Not Pass” signs as part of 

the system. The message board included a script message and 

visual arrow as shown in Figure 3.

Figure 3 – Westbound I-94 Message Board

System Description
3-2

System Description and Operations

• The sensors on the DLM system trailers detected occupancy, which is

a measure of traffic density. As congestion increases, density

increases and thus occupancy increases. The DLM system calculated

an Activity Index based on volume, speed, and occupancy. When

preset Activity Index levels were met, the system sent a signal to the

next upstream dynamic sign to be activated. The greater the

sign/trailer number, the further upstream it was from the lane

closure. The further upstream a sign was from the merge point, the

higher the activity index to trigger activation. This concept is a result

of the changes in traffic conditions, including driver behavior, forced

merges, and associated impacts to traffic flow and queuing

potential. The sign on the trailer closest to the merge point (sign 1)

was always activated.

• Activity Index thresholds are shown in Table 1. When the average

Activity Index exceeded the high threshold based on data at a sensor,

the system activated the next upstream sign and that sign stayed on

until the Activity Index at the next downstream sensor fell below 

the low threshold. For example, when sensor 1 reached an Activity 

Index of 15 percent or higher, the sign on trailer 2 activated until 

the Activity Index for sensor 1 fell below 10 percent. Once activated,

each sign remained activated for a minimum of five minutes.

System

Operations

Table 1 – Sensor Settings

Activity Index Threshold (%) Update

Sensor at Sign Low High Period

Number (minutes)

1 (Base Trailer) 10% 15% 1 minute Closest to the Merge

2 15% 20% 1 minute

3 20% 25% 1 minute

4 25% 30% 1 minute

5 N/A*

• Michigan State Police (MSP) personnel were able to enforce the nopassing zone as needed through a light on the back of each sign

panel as shown in Figure 4. When alerted by the light, officers were

aware that the sign was active and no passing was allowed.

* This sign does not transmit signals because there are no signs upstream of it.
3-3

System Description and Operations

• The MSP assigned an officer to the I-94 work zone throughout

construction. The MSP cited active police presence as the main

deterrent to potential violators. At the I-94 work zone, officers

focused their time on monitoring traffic and responding to traffic

incidents and crashes in the work zone. No citations were written 

on this project, but on other projects using the DLM system many

citations were written. Resource limitations required the officers 

to focus on other areas of this construction project. Active police

presence and enforcement support successful operation of the system.

Figure 4 – Back Side of Dynamic Lane Merge Trailer

Light
3-4

System Description and Operations

• The Concept of Operations diagram for the MDOT system is

presented in Figure 5.

• The subcontractors were responsible for operating and maintaining

the system.

• During early predeployment meetings, MDOT, MSP, and local police

personnel discussed enforcement issues. These agencies determined

that installation of a flashing light on the back of each panel would

alert Highway Patrol personnel when the system was activated and

adequately allow for enforcement of the system.

• MDOT developed a press release, radio advertisements, and

television advertisements for the project to inform the public about

the deployment of the DLM system and educate them on how to

respond to the signs.

• The public was fairly familiar with the system due to its past use by

MDOT on one other project in the Detroit area.

• Because the equipment was leased through the construction

contract, MDOT deployed the DLM system without having to

maintain equipment or store it after use.

• System maintenance was fairly routine and included verifying that

the sensors were operating.

Maintenance

Contractor or

Agency Staff

Coordination with

Key Personnel,

Other Agencies,

and the Public

Figure 5 – Dynamic Lane Merge System Concept of Operations
4-1

Results

• The system accomplished the intended objectives, and MDOT was

pleased with its performance. MDOT had several other previous

experiences with deploying the DLM system. 

• Lessons learned during previous deployments helped MDOT to

develop optimal sensor settings, determine the need to increase

spacing between dynamic signs, and identify locations where use of

the system is warranted by traffic conditions.

• The system was fully operational except for a few days near the end

of construction, when a trailer malfunctioned and was permanently

in flash mode. There were no impacts to traffic based on this

malfunction. Maintenance was completed in about one day and the

system was brought back on line.

MDOT has performed evaluations of selected deployments of the DLM

system in Michigan. The three-to-two merge scenario on I-94 was evaluated,

as were several previous DLM deployments in two-to-one scenarios:

• Based on observations from the I-94 deployment, MDOT estimated

that the DLM system is effective in situations where peak hour 

traffic volumes are approximately 3,000 to 3,500 vehicles per hour

during construction for a three-to-two lane merge. The system is

efficient in situations where the peak hour volume ranges from

3,000 to 3,800 vehicles per hour prior to construction. Some drivers

will choose to avoid the work zone altogether, reducing the hourly

volumes during construction.

• In previous deployments of the two-to-one lane merge, MDOT

identified an effective peak hour volume range of 2,000 to 3,000

vehicles per hour.

• If the deployment site experiences higher or lower volumes than

mentioned above, the DLM system may not be effective. If volumes

are regularly lower than these ranges, a system may not be needed.

If volumes are typically higher than these ranges, the system may be

ineffective at managing queue lengths, or may be active almost

continuously (in which case the same effect could be accomplished

using static signs).

System Performance

System Evaluation
4-2

Results from MDOT’s evaluation of the 2003 I-94 three-to-two merge

project are provided below. The full results of the evaluation are

presented in MDOT’s report.3

• The average number of stops (per probe vehicle run) in the

construction zone decreased from 1.75 to 0.96 during the morning

peak period with the implementation of the DLM system. 

• The stopped time delay during both peak periods and the average

number of stops during the afternoon peak period (per probe

vehicle run) in the construction zone remained relatively unchanged.

• The average morning peak period travel time delay decreased from

95 seconds per vehicle to approximately 69 seconds per vehicle for

every 10,000 feet of travel.

• The average number of aggressive driving maneuvers per travel time

run decreased from 2.88 to 0.55 during the afternoon peak period

and was relatively unchanged during the morning peak period.

• The average travel speed increased from approximately 40 mph to

46 mph during the morning peak period and was relatively unchanged

during the afternoon peak period.

• The DLM system led to a reduction in aggressive driving and

aggressive driving maneuvers during the afternoon peak period,

therefore improving safety at the merge point.

• Crash data were analyzed for 4.3 months during construction but

without the DLM system and 2 months during construction with

DLM. Prior to system activation, there was an average of 1.2 crashes

per month. For the two-month period after the system was

implemented, no crashes were reported. The data included crashes

that occurred within the lane merge transition area.

• MDOT observed that traffic flow was disrupted less by queuing,

leading to less variance of speeds between the two lanes of traffic,

which likely reduced crash risk.

• For the I-94 deployment, the system evaluator, Wayne State

University, determined that the benefits of the system (travel time

savings and vehicular fuel savings) outweighed the costs if the value

of time for delayed motorists is greater than $3.33 per hour. Wayne

State University determined this value by multiplying a monetary

value (an iterative process) by the travel time savings, adding in the

fuel savings, and then comparing this value to the actual cost of the

system. This finding showed that even if a delayed motorist’s time

was only valued at a rate of $3.33 per hour, which is a low value for

Safety

Cost Savings

Results

Benefits/Impacts

Mobility

3Michigan Department of Transportation (2004). Development and Evaluation of an Advanced

Dynamic Lane Merge Traffic Control System for 3 to 2 Lane Transition Areas in Work Zones. 
4-3

Results

4U.S. DOT (2003). Valuation of Travel Time in Economic Analysis.

http://ostpxweb.dot.gov/policy/Data/VOTrevision1_2-11-03.pdf

user delay time, the system was cost-effective. As the value of a

motorist’s time is increased from $3.33 per hour, the benefits of the

system would increase due to greater travel time savings and would

further outweigh the system costs. User delay time is usually valued

at a much greater amount than $3.33 per hour. For a relative

example of delay analysis, note that the U.S. Department of

Transportation uses an average dollar figure of $11.20 per hour for

each person in a car and $18.10 per hour for a truck driver when

calculating user cost of delay.4

• Through informal channels, MDOT recognized a positive perception

of the system by the public. Because the system had been deployed

previously, the public had become familiar enough with the system

to lessen the need for citations to achieve compliance with the 

no-passing zone.

• The DLM system can be helpful in increasing safety and reducing

delay near work zones where lane closures are necessary. 

• Sites should be wide enough to allow trailers to be moved in and

out, and allow for safe placement off the roadway. Site width is also

important for enforcement activities.

• MDOT held several meetings with key stakeholders, including the

law enforcement community, to keep them involved in system

planning and design. Identifying stakeholders early in the planning

stage is one of the key steps to a successful implementation.

• It is better to use the DLM system on construction projects where the

work zone geometry and location do not change frequently because

such changes often require recalibrating the detectors. Long-term,

large projects may have phases that are static, where the system can

remain in place for a longer time. 

• It is important to give the driving community time to adapt to the

system so that they will know how to comply with the regulatory

signs in the DLM-controlled area.

• The system requires line of sight between sensors for adequate

communication. MDOT raised antennas on the trailers due to line of

sight issues.

Public Reception/

Reaction 

to the System

Obstacles

Encountered and

Lessons Learned

General

Relating with 

Other Agencies

System Features/

Capabilities

Communications
4-4

• It is important to use a proactive approach to building public

awareness of an ITS deployment. Successful techniques include

meeting with stakeholders, holding press conferences, issuing news

releases, and keeping local media up to date. MDOT used all of the

above-mentioned techniques, and also met frequently with law

enforcement early on to avoid miscommunication on overall system

objectives.

• It is necessary to allow for access to sensor stations for maintenance.

• When changes in work zone roadway geometry are made, it is

important to allow time for drivers to learn the new setup.

• Stations may need to be reset manually when there are power

interruptions.

• The implementing agency can meet maintenance needs solely

through use of the vendor, or the agency can maintain the system

with initial help from the vendor. Sensor power issues caused some

small delays early on for MDOT. The system will require an adequate

system maintenance plan to avoid large amounts of system

downtime.

Maintenance

System Operations

System Deployment

Results

“The public expects

us to do everything

we can to alleviate

the effects of 

work zones, and

innovative solutions

like this one are

important to

achieving that goal.”

– Robert J. Cannon

Supervisor

Clinton Township

Michigan
Federal Highway Administration Resource Center Locations

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5-1

Conclusion

MDOT has successfully deployed the dynamic lane merge system on

several projects, including I-94 in a suburb of Detroit, to help smooth

traffic flow and reduce aggressive driving just prior to the construction

area. MDOT observed a decrease in aggressive maneuvers and average

peak period travel time. These factors influenced both mobility and

safety in a positive manner, and ultimately satisfied the goals of the

deployment.

Michigan DOT contact 

for this project 

Jeff Grossklaus, P.E.

Construction Staff Engineer

Michigan Department of 

Transportation

Construction and 

Technology Support Area

P.O. Box 30049

8885 Ricks Rd.

Lansing, MI 48909

517-322-5769

grossklausj@michigan.gov
THIS DOCUMENT IS ONE IN A SERIES OF PRODUCTS THAT ADDRESS

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• Freeway and Arterial

Management

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and Maintenance

• Planning and Integration

• Real-Time Traveler Information

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Information

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Travelers and Maintenance

• Work Zones

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