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Technical Report Documentation Page

1. Report No.

FHWA-HOP-14-020

2. Government Accession No. 3. Recipient’s Catalog No.

4. Title and Subtitle

Ramp Metering: A Proven, Cost-Effective Operational Strategy—A 

Primer

5. Report Date

October 2014

6. Performing Organization Code

7. Author(s)

Arianne Mizuta, Kim Roberts, Les Jacobsen, Nick Thompson

8. Performing Organization Report No.

9. Performing Organization Name And Address

Parsons Brinckerhoff

999 Third Avenue, Suite 3200

Seattle, WA 98104

Under contract to Cambridge Systematics, Inc.

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTFH61-12-D-00048 T-13002

12. Sponsoring Agency Name and Address

U.S. Department of Transportation

Federal Highway Administration

Office of Operations

1200 New Jersey Ave S.E.

Washington, D.C. 20590

13. Type of Report and Period Covered

Primer

14. Sponsoring Agency Code

FHWA HOP

15. Supplementary Notes

James Colyar, FHWA Government Task Manager

16. Abstract

This primer poses ramp metering as a potential tool to address commonly occurring congestion and safety issues. 

Despite initial opposition and skepticism from various stakeholders, ramp metering has been deployed, sustained, 

and even expanded in many regions. This primer incorporates recent research on challenges agencies experience 

during their attempts to deploy or expand ramp metering in their regions. 

While geometric limitations of existing ramps are a common challenge, agency support and project costs also 

pose difficulties for several agencies. Recent case studies provide insights into how these common challenges 

could be addressed as well as lessons learned. This primer emphasizes organizational capability, public outreach, 

and geometric limitations as key considerations when deploying or expanding ramp metering.

17. Key Words

Ramp Metering, Ramp Management, Freeway 

Management, Active Traffic Management 

(ATM), Active Transportation and Demand 

Management (ATDM), Intelligent Transportation 

Systems (ITS), Transportation Systems 

Management and Operations (TSM&O)

18. Distribution Statement

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

32

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer i

TABLE OF CONTENTS

1. OVERVIEW OF RAMP METERING --------------------------------------1

1.1 What Is Ramp Metering?-----------------------------------------2

1.2 Ramp Metering and Transportation Systems 

Management and Operations------------------------------------3

1.3 Ramp Metering Goals and Objectives-------------------------3

1.4 History of Ramp Metering ---------------------------------------3

1.5 Benefits of Ramp Metering--------------------------------------5

1.6 Why Ramp Meters Are Effective-------------------------------6

1.7 Ramp Metering Analysis Tools---------------------------------7

1.8 Ramp Metering Control Approaches --------------------------7

1.9 Ramp Metering Components------------------------------------9

1.10 Ramp Metering Algorithms--------------------------------------9

2. RAMP METERING CHALLENGES ------------------------------------- 11

2.1 Geometry of Existing Infrastructure ------------------------- 11

2.2 Costs and Funding----------------------------------------------- 12

2.3 Public Opposition------------------------------------------------ 12

2.4 Heavy Ramp Volume ------------------------------------------- 12

2.5 Local Agency Opposition -------------------------------------- 13

2.6 Lack of Agency Support --------------------------------------- 13

3. KEYS FOR SUCCESSFUL RAMP METERING 

DEPLOYMENT OR EXPANSION---------------------------------------- 14

3.1 Is Ramp Metering Right for You?---------------------------- 14

3.2 Getting Ready for Ramp Metering --------------------------- 15

3.3 Operating Ramp Metering Effectively ---------------------- 18

4. GOING ABOVE AND BEYOND ----------------------------------------- 21
ii October 2014

Figures

Figure 1: Ramp metering configuration----------------------------------------- 2

Figure 2: Ramp metering within freeway management and 

TSM&O---------------------------------------------------------------- 3

Figure 3: Ramp metering in the top U.S. metropolitan areas --------------- 4

Figure 4: Select regional benefits of ramp metering-------------------------- 5

Figure 5: Comparison of mainline conditions with and without 

ramp metering—provided by WSDOT ------------------------- 6

Figure 6: Duration of occupancy at shutdown capacity before 

and after ramp metering -------------------------------------------- 6

Figure 7: Identified barriers to ramp metering deployment ----------------11

Figure 8: Example of challenging geometrics for ramp metering---------12

Figure 9: Ramp metering deployment decision process flow--------------14

Figure 10: Typical sign used to convert single lane on-ramp into 

dual-lane queue storage or allow conditional use of 

the shoulder.----------------------------------------------------------18

Figure 11: Dimensions of performance monitoring -------------------------19

Figure 12: Ramp metering deployment challenges and mitigation 

strategies--------------------------------------------------------------20

Tables

Table 1: Summary of ramp metering approaches ----------------------------- 8

Table 2: Description of example algorithms ----------------------------------10
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer iii

LIST OF ABBREVIATIONS AND SYMBOLS

ATDM Active Transportation and Demand Management

Caltrans California Department of Transportation

CARMA Corridor Adaptive Ramp Metering Algorithm

FDOT Florida Department of Transportation

FHWA Federal Highway Administration

HCM Highway Capacity Manual

HOV high-occupancy vehicle

ITS Intelligent Transportation Systems

MnDOT Minnesota Department of Transportation

ODOT Oregon Department of Transportation

SWARM System-Wide Adaptive Ramp Metering

SZM Stratified Zone Metering

TOPS-BC Tool for Operations Benefit/Cost

TRB Transportation Research Board

TSM&O Transportation Systems Management and Operations

WSDOT Washington State Department of Transportation

Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 1

“Our region first installed ramp 

metering in our state’s largest 

urban area in the 1980s and we 

have steadily expanded the 

system since then. Other, smaller 

cities in our state have seen the 

benefits and are planning ramp 

meter systems.”—Pete Briglia, 

former WSDOT and TRB Freeway 

Operations Committee Chair

1. OVERVIEW OF RAMP METERING

Due to the growth of metropolitan areas and tightening of fiscal belts, 

the need for effective and financially viable freeway management tools 

is unprecedented. This primer poses ramp metering as a potential tool 

to address commonly occurring congestion and safety issues. Despite 

initial opposition and skepticism from various stakeholders, ramp 

metering has been deployed, sustained, and even expanded in many 

regions. This primer incorporates recent research on challenges 

agencies experience during their attempts to deploy or expand ramp 

metering in their regions. 

While geometric limitations of existing ramps are a common challenge, 

agency support and project costs also pose difficulties for several 

agencies. Recent case studies provide insights into how these common 

challenges could be addressed as well as lessons learned. This primer 

emphasizes organizational capability, public outreach, and geometric 

limitations as key considerations when deploying or expanding ramp 

metering.
2 October 2014

1.1 What Is Ramp Metering?

Ramp meters are traffic signals installed on freeway on-ramps to 

control the frequency at which vehicles enter the flow of traffic on the 

freeway. Ramp metering reduces overall freeway congestion by 

managing the amount of traffic entering the freeway and by breaking 

up platoons that make it difficult to merge onto the freeway. As seen in

Figure 1, vehicles traveling from an adjacent arterial onto the ramp 

form a queue behind the stop line. The vehicles are then individually 

released onto the mainline, often at a rate that is dependent on the 

mainline traffic volume and speed at that time. The configuration in the 

diagram is the most common; however, some agencies have altered this 

design to accommodate transit and high-occupancy vehicle (HOV)

policies or existing geometric limitations. 

Figure 1: Ramp metering configuration
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 3

1.2 Ramp Metering and Transportation Systems Management 

and Operations

Ramp metering is one of many strategies in the realm of freeway 

management and operations that agencies use to operate the existing 

freeway network at full potential. Successful operation of ramp 

metering systems leads toward integration with other activities that 

actively manage the freeway network. Transportation Systems

Management and Operations (TSM&O) is an 

integrated program, with strategies such as 

ramp metering, road weather management, and 

incident management (Figure 2), that requires 

continuous and active management by agencies 

to ultimately provide optimized system 

performance to existing freeway infrastructure. 

The end result is a program that will improve 

mobility, reliability, safety, and environmental 

impacts while preserving freeway capacity at a 

significantly lower cost than traditional 

capacity improvements. Ramp metering can 

also support regional congestion management 

processes.

1.3 Ramp Metering Goals and Objectives

An agency’s goals and objectives for ramp 

metering should be consistent with regional 

transportation goals and objectives, which will 

vary from region to region. Often these goals 

and objectives are driven by the needs and 

areas of opportunity for a region. For instance, 

one region may want to improve safety and 

another may prioritize increasing mainline 

speed. Alternatively, some regions may want to encourage HOV and 

transit use. Some common priorities among agencies are safety, 

mobility, quality of life, environmental effects, and motorist 

perceptions and satisfaction. With a set of objectives in place, agency 

decisions, such as what kind of system or algorithm should be used, 

will be appropriately focused.

1.4 History of Ramp Metering

Ramp metering was first deployed in the 1960s on the Eisenhower 

Expressway in Chicago. In the subsequent years, ramp meters were 

deployed in major metro areas such as Detroit, Los Angeles, and 

Figure 2: Ramp metering within freeway 

management and TSM&O
4 October 2014

Minneapolis/St. Paul as experiments in increasing driver speeds during 

peak travel periods while reducing travel times and the frequency of 

freeway crashes. As ramp metering strategies and techniques advanced, 

more metro areas across the U.S., as well as Europe and Australia, 

began implementing ramp metering systems. 

The uniqueness of the cities furthered the advancement and refinement 

of ramp metering as a traffic management strategy. The different

agency needs and priorities resulted in various strategies, such as 

preferential treatment for HOVs and transit through the designation of 

bypass lanes, special ramp treatments like metering multiple lanes 

(including ramp shoulders), and metering two or three vehicles per 

green. As displayed on Figure 3, ramp metering has been deployed in 

varying degrees of sophistication and scale across the U.S.

Figure 3: Ramp metering in the top U.S. metropolitan areas
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 5

Select environmental impacts:

• Minneapolis identified a net 

annual savings of 1,160 tons 

of emissions.*

• Other simulation analysis 

shows ramp metering to be 

effective in reducing CO 

emissions by 1,195 tons per 

year

*emission values calculated based 

on a simplified approach on 

average changes in speed.

1.5 Benefits of Ramp Metering

When agencies implement effective ramp metering programs using 

strategies suitable to the region, they often realize significant, longterm benefits. While the magnitude of the benefits may vary depending

on the level of congestion and configuration, common benefits persist 

across many regions. The widespread benefits of ramp metering, 

relative to its costs, make it one of the most cost-effective freeway 

management strategies. 

Mobility, Reliability, and Efficiency

Ramp metering reduces mainline congestion and overall delay, while 

increasing mobility through the freeway network and traffic 

throughput. Travel times, even when considering time in queue on the 

ramp, are generally reduced when ramp metering is implemented. 

Travel time reliability has become an important measure of ramp 

metering effectiveness. Many regions have experienced increased 

travel time reliability (reduced variations in day-to-day travel times)

due to ramp metering.

Safety

Ramp meters help break up platoons of vehicles that are entering the 

freeway and competing for the same limited gaps in traffic. By 

allowing for smooth merging maneuvers, collisions on the freeway can 

be avoided. Many regions have reported significant reductions in crash 

rates after starting ramp metering. 

Effective ramp queue management can prevent queues from spilling 

onto the adjacent arterial and clogging up the city street network with 

stopped vehicles that are waiting to enter the freeway.

Reduced Environmental Impacts

Ramp meters smooth the flow of traffic entering the freeway so 

vehicles can merge with mainline traffic with minimal disruption to 

traffic flow. Eliminating prolonged periods of stop-and-go conditions 

due to congestion can reduce vehicle emissions and fuel consumption 

on the freeway. It can be argued that emissions and fuel consumption 

increase at the ramp meter, which is why the environmental analysis 

must be sensitive to actual ramp operations and fuel estimation 

methodologies, especially with the prevalence of electric and hybrid 

vehicles on the roadway.

Figure 4: Select regional benefits 

of ramp metering

Source: FHWA Ramp Management and 

Control Handbook
6 October 2014

Though it is typically difficult to measure, many regions have attributed 

reductions in carbon emissions and fuel consumption to ramp metering 

implementation.

Benefit Versus Cost

A benefit/cost analysis is a comprehensive 

analysis to evaluate and compare the cost 

effectiveness of ramp metering implementation 

and operation against the “no ramp meter” 

condition. The measured benefits of implementing 

ramp metering systems can outweigh the 

associated costs by a ratio of 15 to 1, as concluded 

in the Twin Cities Ramp Meter Evaluation. A 15 

to 1 benefit/cost ratio is excellent for 

transportation improvements.

1.6 Why Ramp Meters Are Effective

Without ramp meters in operation, multiple 

vehicles merge in tightly packed platoons, causing 

drivers on the mainline to slow down or even stop 

in order to allow vehicles to enter. The cascading 

slower speeds, both on the mainline and on the 

ramp, quickly lead to congestion and sometimes 

stop-and-go conditions. Ramp meters can break up 

the platoons by controlling the rate at which 

vehicles enter the mainline from the ramp, as 

shown on Figure 5. This allows vehicles to merge 

smoothly onto the mainline and reduces the need 

for vehicles on the mainline to reduce speed. In 

addition to breaking up platoons, ramp meters help 

manage entrance demand at a level that is near the 

capacity of the freeway, which prevents traffic 

flow breakdowns. Ramp meters are shown to 

reduce peak hour lane occupancies (i.e., freeway 

density) and quicken recovery from mainline 

breakdown back to or below the critical occupancy 

threshold, as shown on Figure 6. Typical results 

include reductions in travel time, reductions in 

crash rates, and increased traffic speed.

Figure 5: Comparison of mainline conditions with 

and without ramp metering—provided by 

WSDOT 

Figure 6: Duration of occupancy at shutdown 

capacity before and after ramp metering
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 7

1.7 Ramp Metering Analysis Tools 

The technology utilized by ramp meters has evolved to offer increased 

scalability, efficiency, and customization. Through developed 

simulations and databases, agencies can model the effects of ramp 

metering on their existing freeway operations. These exercises can aid 

in the decision-making and planning process when planning for ramp 

metering deployment or expansion.

Simulation models can aid in determining what control algorithm 

would be most appropriate to manage freeway congestion based on 

user-defined inputs on system conditions. Computer-based simulations 

can estimate a set of traffic measures, such as travel time speed, for a 

given freeway corridor. The simulations can use new operational 

strategies like adaptive ramp metering coded directly into the software 

so that realistic environments can be evaluated for a proactive approach 

to congestion management.

Optimal ramp meter operations require robust data collection and 

analysis. Data regarding traffic volumes, travel times, and other

appropriate performance measures should be collected, modeled, and 

analyzed both before and after ramp meters are installed. Volume data 

is collected in the form of video or loop detection along the ramp and

on the freeway mainline upstream and downstream of the ramp.

An integrated database, that contains data such as roadway inventory, 

detector data, traffic counts, crash records, and incident records, can 

streamline the process to evaluate the effectiveness of various ramp 

metering strategies or algorithms. The evaluation database not only 

reduces the effort to collect all these data sets independently, but can be 

used with enhanced data sets and could provide the data needed to 

support visualization of various ramp metering scenarios.

1.8 Ramp Metering Control Approaches 

Depending on the existing infrastructure, constraints, or objectives of 

the ramp metering program, an agency may select various ramp 

metering approaches. Table 1 provides details on various levels of 

control, including appropriate situations to use each approach. The 

following is a high-level overview of commonly used control 

approaches for ramp metering:
8 October 2014

Single or Multi-Lane Metering—Single lane metering allows only one 

vehicle to enter the freeway during each signal cycle. Multi-lane 

metering requires two or more lanes to be provided on the ramp and a 

signal head dedicated to each lane. After the stop bar, the lanes are 

required to merge into a single lane before merging onto the freeway.

Single or Dual Release Metering—One vehicle per green (or single 

release metering), operates with a shorter green time than with a two 

vehicles per green (or dual release) approach. Dual release allows for 

two vehicles to enter the freeway each cycle but requires a longer green 

time. The dual release metering approach usually increases ramp 

capacity under metering.

Freeway-to-Freeway Connections—Ramp metering on freeway-tofreeway ramps is less common due to the high travel speeds and the 

perceived increased potential for vehicle collisions because of vehicle

queues where drivers may not expect them. Geometric constraints also 

exist such as limited sight distance along a curved roadway and limited 

provisions to provide the required storage for queued vehicles on 

ramps. Freeway-to-freeway metering, if possible, can significantly 

improve the ability to manage traffic on a freeway because a greater 

share of entering traffic is controlled by meters.

Bypass Lanes—Bypass lanes allow a specific class of vehicle (usually 

an HOV, a bus, or, in some locations, a truck) to avoid delay at ramp 

meters and have the right of way to merge directly on to the freeway. 

Table 1: Summary of ramp metering approaches
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 9

Bypass lanes may have a single detection loop, actuations of which 

could incrementally increase the length of the ramp meter cycle each 

time a vehicle is detected.

1.9 Ramp Metering Components 

Ramp metering requires some essential components and equipment in 

order to operate safely and effectively. Configuration, communication, 

and safety are objectives agencies should consider when placing signal 

heads, detectors, and signs. The following are key components in most 

ramp metering setups:

Signal Heads—The signal heads used for ramp metering are either twosection or three-section heads. Two section heads have green and red 

indications. Three section heads include the yellow indication and may 

be more familiar to most drivers. 

Detectors—Detectors are necessary to monitor condition on the ramp 

and mainline. For instance, the signal should only turn green when a 

vehicle is detected at the stop bar. Queue detectors can also be used to 

monitor and manage queue length when placed upstream of the stop 

bar. Detectors can also monitor demand on the mainline and merge 

points to aid in determining the metering rate. Detection equipment on 

the ramps themselves (such as stopbar located demand detectors)

should be connected directly to the ramp controller cabinet. 

Signage—Signs should be placed at the start of the ramp and near the 

signal head. The sign content can provide instruction to vehicles when 

they enter the ramp and at the signal. Upstream signs with lights or 

adaptive screens can also indicate whether the ramp is being metered at 

a given time. Proper signage will facilitate clear communication and 

compliance with the established system. 

1.10 Ramp Metering Algorithms

There are a wide range of ramp metering control strategies and

algorithms. The three primary types of control strategies are fixed time, 

local control, and system-wide control. Fixed time metering is the 

simplest approach in terms of implementation because it has no 

reliance on traffic detection or communication with a Traffic 

Management Center. However, it is also the most rigid since it cannot 

make adjustments to the metering rate based on changing real-time 

mainline or ramp conditions. Both system-wide and local traffic 

responsive control rely on loop detectors or other forms of traffic 

surveillance to select metering rates. A local control strategy will select 

metering rates based on traffic conditions present on the ramp and at 
10 October 2014

adjacent mainline locations to remedy isolated congestion or safetyrelated problems. Local control cannot factor in conditions at adjacent 

ramps or throughout the freeway mainline. Local control is often used 

as a back-up strategy when system-wide algorithms are offline or 

communications are inoperable. System-wide control is responsive to 

both local and corridor-wide real-time traffic conditions. When 

calculating a metering rate, system-wide control takes into account 

traffic conditions upstream and downstream from an individual ramp 

along a specific freeway segment or along an entire corridor. Systemwide control provides more options in optimizing mainline capacity 

and reducing the amount of overall system delay by using multiple 

ramps to control traffic at any given bottleneck or congested location. 

Descriptions of example algorithms are included in Table 2.

Table 2: Description of example algorithms
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 11

Thinking about expansion?

Agencies considering expansion 

or further development of their 

ramp metering program should 

first assess the current state of 

the program. In particular, the 

agencies should evaluate current 

performance metrics in order to 

target areas of opportunity and 

set expectations for 

improvement. The impact of the 

proposed expansion should be 

reported and shared with 

relevant stakeholders.

2. RAMP METERING CHALLENGES

Though ramp metering has proved a successful strategy in many cities, 

agencies continue to face barriers and other opposition in their attempts 

to deploy or expand their ramp metering systems. In a survey of the top 

metro areas, the barriers cited by agencies displayed common themes,

such as lack of support—whether financial or political—and existing 

infrastructure that was not compatible with ramp metering.

Figure 7 shows the most common barriers to development from the 

survey. 

Typically, regions with existing ramp metering systems will see areas 

of opportunity where ramp metering could be further deployed to 

improve freeway operations.

Of the regions that already have ramp meters in operation, many cited 

barriers to expanding their current system. The most prevalent barrier 

was the geometric limitations of the existing ramps (58 percent), with 

capital costs (42 percent) and operations and maintenance costs 

(26 percent) also frequently cited. The ability to maintain the system 

infrastructure and the technical skills of the existing staff were seen as 

barriers in 16 percent of the regions. Public opposition and local agency 

opposition was cited by 11 percent of regions as barriers to expansion.

2.1 Geometry of Existing Infrastructure

Some agencies have stated that ramp metering is not possible in their 

region due to the configuration and structure of their ramps. Because 

ramp metering requires space for vehicles to merge into mainline traffic 

and to wait in a queue, not all ramp configurations are suitable for ramp 

metering. Key geometric issues that should be considered when 

investigating ramp metering include inadequate acceleration length, 

mainline weaving problems due to closely spaced ramps, and limited 

sight distances on a horizontal or crest vertical curve. Ramp metering 

can reduce the impact of geometric conditions that cause problems 

under high speed or high volume ramp conditions and heavy mainline 

volumes because the ramp speeds are likely to be lower and there is 

less disruption from vehicle platoons vying for limited mainline gaps.

Figure 7: Identified barriers to 

ramp metering deployment 
12 October 2014

Figure 8: Example of challenging geometrics for ramp metering

For instance, if an on-ramp lane 

merges too abruptly, the short 

distance past the stop bar may create 

unsafe conditions leaving inadequate 

space for vehicles to accelerate to a 

safe speed in comparison to the 

mainline. Figure 8 illustrates common 

geometrics that pose challenges to 

ramp meter implementation. In 

addition, narrow configurations may 

not have adequate shoulder space for 

an HOV bypass lane, a transit bypass

lane, or an enforcement zone where 

compliance can be monitored.

2.2 Costs and Funding

Despite the benefits of ramp metering, 

there are monetary costs for deploying 

and maintaining ramp metering systems. Without sufficient and welltimed funding, ramp metering deployment may be unsuccessful and not 

realize its full benefits. When agencies attempt to procure funding for 

ramp metering programs from local, state, or federal governments, they 

are often competing with other initiatives that may have greater priority 

or support. As exhibited in recent survey results, most agencies desire 

expansion of their ramp metering system following the initial 

deployment, which would require additional funds.

2.3 Public Opposition

The support of the public is often critical in the deployment and 

expansion of ramp metering. Many agencies encountered public 

opposition that significantly deterred or completely halted efforts to 

deploy ramp meters. Often this opposition is rooted in misconceptions 

about ramp metering and its effectiveness. The public may also raise 

concerns about equity, claiming that ramp metering asymmetrically 

favors those who live outside the city center.

2.4 Heavy Ramp Volume

As a ramp meter regulates the flow of vehicles entering the mainline, 

cars form a queue on the ramp behind the signal. If the meter’s release 

rate is less than the rate at which vehicles approach the ramp, the queue 

will lengthen. If too long, a queue could spill onto arterials resulting in 

inefficient arterial operations. Ramps that are shorter in length or have 
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 13

Lessons learned

• Agencies should consider 

suitability and feasibility prior 

to deploying ramp metering

• Public should be involved in 

ramp metering planning and 

development process

• Ramp metering requires 

continuous monitoring, even 

following deployment

less storage space are at a higher risk of arterial backup than long ramps 

with similar demand.

2.5 Local Agency Opposition

Deploying or expanding ramp metering systems often impacts a variety 

of stakeholders including arterial agencies and local businesses. These 

groups may have a negative perception of ramp metering and may have 

the resources to halt efforts to deploy or expand ramp metering. Local 

agencies are often concerned that the ramp queues will negatively 

affect their transportation systems. Local agencies, like the public, may 

also be concerned about equity issues. Conversely, such groups would 

be valuable allies in building support for ramp metering and ensuring 

smooth operations.

2.6 Lack of Agency Support

Sometimes there may be a lack of support from the agency with 

responsibility for freeway operations. There could be many reasons for 

this lack of support. Sometimes it is because key people in the agency 

do not understand ramp metering. They may not be aware of the 

benefits of ramp metering and the high benefit/cost ratio that ramp 

metering projects show. It may also be because there is a concern over 

long term maintenance and operations costs. Agency staffing may also 

be an issue, either there is not sufficient staff or there is not staff with 

the needs skills and knowledge to implement or operate ramp metering. 

Consistent and clear communication and information can often increase 

agency support.
14 October 2014

3. KEYS FOR SUCCESSFUL RAMP METERING

DEPLOYMENT OR EXPANSION

Whether an agency is expanding its already robust system or deploying 

ramp meters for the first time, there are key components of the planning 

and implementation process that it should keep in mind.

3.1 Is Ramp Metering Right for You?

The agency attempting to start new projects or 

deploy new systems should have an 

understanding of the high-level regional and 

agency goals, both short-term and long-term. 

New projects, including ramp metering 

deployment, should contribute to and 

complement existing initiatives and adhere to 

high-level objectives.

Ramp metering should be deployed with purpose 

to address existing operational issues (Figure 9). 

The primary issue ramp metering can mitigate is 

recurring mainline congestion; however, the

agency may also want to increase safety at 

merge points and on the mainline and control 

mainline access during construction activities, 

special events, or traffic incidents. All of these 

issues have the potential to be aided through 

ramp metering and are valid reasons to pursue 

this strategy. However, if these issues are not 

present in the region or corridor, ramp metering 

is not an applicable strategy and should not be 

pursued.

Once the agency determines that its issues are 

relevant to ramp metering, it must determine if 

ramp metering is a feasible strategy to pursue. It can conduct feasibility 

studies to allocate resources efficiently and determine where ramp 

meters would be effective. Through evaluating outcomes from 

feasibility studies, it can discern whether or not a ramp meter is 

warranted at a particular location and get a preliminary glimpse into the 

potential effectiveness and magnitude of benefits.

Benefit/cost analysis is an additional tool that assigns a dollar value to 

the expected costs and benefits of ramp metering, which can determine 

and communicate the value of the project. Because the agency may 

Figure 9: Ramp metering deployment decision 

process flow
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 15

What is in 23 CFR 940?

Systems Engineering Analysis

• Identification of portions of 

regional or statewide ITS 

architecture implemented

• Identification of participating 

agencies and other 

stakeholders

• Operational concept

• Agreements required for 

implementation

• System functional 

requirements

• Interface requirements

• Identification of ITS standards

• Sequence of projects required 

for implementation

face operations, maintenance, and capital costs as barriers, a benefit/

cost analysis that yields a high ratio or positive net present value will 

provide leverage when seeking or appropriating funds. This type of 

analysis can be applied to a variety of constraints and scenarios, 

making it scalable to numerous regions that want to investigate ramp 

metering. Furthermore, this technique can be used for initial 

deployment and to measure the incremental benefit of expanding or 

improving a ramp metering system for ongoing performance reporting.

The agency should also assess its organizational capabilities and 

evaluate whether it is mature enough to undertake ramp metering 

deployment. Ramp metering deployment requires the operating agency 

to perform a multitude of tasks. Agency assessment can often identify 

strengths and areas that need strengthening. Agency assessment will 

prioritize areas of improvement by evaluating the internal capability to 

successfully implement ramp metering according to various 

organizational dimensions. The TSM&O capability maturity model is 

an assessment tool that identifies six dimensions of capability in which 

the agency can determine its level of maturity.

If the results from these various exercises indicate ramp metering is 

both appropriate and feasible, then the agency should take the next step 

in moving toward ramp metering deployment, which includes making 

sure that ramp metering projects are in the agency transportation plan

and program.

3.2 Getting Ready for Ramp Metering

A systems engineering approach should be taken on all ramp metering 

projects, as required by FHWA Final Rule 23 CFR 940 for federally 

funded ITS projects to conform to the National ITS Architecture and 

standards. Going through the systems engineering process in the project 

development stage can guide the agency through the procurement, 

construction, fabrication, and systems acceptance phases of a project. 

An agency can tailor and scale the “V" systems engineering model, the 

FHWA preferred model for ITS projects, to fit the complexity of a 

project. One of the primary benefits in following these processes is 

early stakeholder involvement, the coordination with regional ITS 

architectures, and identification of interface points. Although systems 

engineering may require more effort at the beginning than would be 

conducted otherwise, the end result is a ramp metering system that is 

highly functional, efficient, has a reduced risk of failure, and one that 

can evolve with a minimum level of redesign and cost.
16 October 2014

SPOTLIGHT

FDOT’s steps for training and

operational readiness

• Management and Operations 

Staff Training

• Operator Training

• Field Technician Training

• Actions required to be 

operationally ready for turnon:

− Develop or finalize 

operational strategies

− Assessment of operational 

readiness

− Performance monitoring

• Recommended outreach 

activities needed prior to 

turn-on:

− Public & media 

communication

− Leadership outreach

Challenges addressed

• Lack of agency support

• Public opposition

• Equity imbalance

• Lack of backing materials to 

promote expansion

SPOTLIGHT

WSDOT public outreach

The detailed public involvement 

plan started three to five years 

prior to ramp meter activation 

and continued through one year 

after turn-on, with multiple 

objectives like increasing driver 

education and acceptance of the 

system, address enforcement 

issues, and allowance for design 

changes prior to construction 

stemming from driver knowledge 

of neighborhood issues. 

To define project costs and a timeline, the agency should identify 

staffing and training needs and create specific procedures for testing, 

installing, and maintaining software systems and field devices if these 

procedures are not already established through previous ramp metering 

deployments. These procedures are key concepts in the systems 

engineering process.

Traffic data collection prior to and after ramp meter installation 

measures the benefits of the implemented ramp metering strategies. 

A consistent approach to collecting, modeling, and analyzing traffic 

volumes, travel times, and other performance measures should be 

established early in the project development process.

Agencies, such as FDOT, are finding success with established 

procedures to guide management through the ramp metering 

implementation process. 

Gain public and agency support 

Because negative perceptions held by the public and other local 

agencies can hinder ramp metering deployment or expansion, the 

agency should devote efforts to outreach and collaboration. 

To familiarize the public with ramp metering and to encourage their 

support, the agency should conduct outreach that proactively 

disseminates information to the public and clearly communicates the 

benefits of ramp metering. These efforts may include gathering public 

feedback, answering questions from the public, conducting focus 

groups and open houses, and issuing statements to local media. In order 

to reach a broader local population, the agency should maintain FAQs 

and other important information on a website and distribute this 

information via brochure or flyer. Providing clear information and 

addressing questions adds transparency to the planning process, which 

the public will generally favor. The agency could address stakeholder 

misconceptions of actual or perceived operations and maintenance

costs by a thorough evaluation of costs associated with operating and 

maintaining ramp metering systems.

Local officials and interest groups can be instrumental in gaining 

widespread support. The agency should reach out to local officials to 

communicate the benefits of ramp metering and collaborate to address 

potential and existing issues. 

Inter-agency cooperation is essential for early and on-going 

coordination. Inter-agency support can be won by assembling and 

providing supporting information that justifies the need for ramp meter 
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 17

Benefit/cost analysis web 

resources

FHWA Operations Benefit/Cost 

Analysis Desk Reference web site: 

provides guidance, tools, and 

information for conducting 

benefit/cost analysis for a wide 

range of TSM&O strategies and 

projects (ops.fhwa.dot.gov/

publications/fhwahop13004/)

U.S. Department of Transportation 

Research & Innovative Technology 

Administration ITS Joint Programs 

Office Knowledge Resources web 

site: users can browse benefits 

and costs from various projects

(www.itsknowledge

resources.its.dot.gov/)

deployment or expansion. The agency can develop agreements among 

each other to address known concerns, which can be a mutually 

beneficial relationship. For instance, a key element of successfully 

ramp metering is driver compliance. Transportation agencies should 

work with enforcement agencies to develop a cohesive enforcement 

plan.

Identify costs and funding sources

The agency can utilize FHWA tools, such as the USDOT Knowledge 

Resources website, to identify capital costs related to the installation of 

new systems. FHWA tools can also be used to identify and estimate

corresponding benefits to be used in funding and programming 

decisions. The agency can strengthen its case for deploying ramp 

metering by itemizing specific costs, thus increasing transparency.

Providing benefit and cost information can help strengthen the case for 

ramp meter expansion by showcasing the benefits and providing 

leverage for requesting funds. 

In order to secure funding, the agency must communicate the high 

priority of ramp metering to authorities. In agency budgeting processes, 

provisions for ramp meter installation should be included in future 

construction planning efforts.

Understand traffic conditions and volumes on ramps, mainline, 

and arterials

Successful ramp metering requires an understanding not only of the 

ramp conditions but also the conditions and volumes of the mainline 

and surrounding arterials. Thus, the agency should monitor the ramp, 

mainline, and arterial conditions to inform ramp metering policies, 

procedures, and strategies.

When evaluating mainline conditions, the agency should identify

segments of freeway that show congestion forming near particular ramp 

locations. Metering these ramps can balance mainline volumes within 

the segment and reduce overall congestion. The impact of queue 

spillover on the local road network is potentially disruptive for arterial 

traffic flow and poses problematic merging and turning situations. The

agency should collaborate with the arterial signals operators to enhance 

safety and effectiveness of ramp meters through signal timing, arterial 

striping, and ramp metering rates to manage queue backup.
18 October 2014

Challenges addressed

• Long ramp queues

• Arterial backups

• Violation rates

Consider queue lengths and delay

Upon observation of system-wide traffic conditions, and the collection 

and analysis of traffic volumes at each ramp, an agency can determine 

whether or not they need to implement queue management strategies at 

single or multiple ramp locations. 

The queue length on the ramp will be impacted by both the mainline 

and arterial traffic conditions. While queue management is a key 

consideration for optimizing freeway operations, the amount of time 

spent in a ramp meter queue generally adds to negative public 

perception. Queue management is closely related to the geometric 

limitations of the existing ramps, so both should be considered when 

exploring options. Two approaches to address queue length are 

increasing queue storage through lengthening the ramp or widening the 

ramp through adding pavements or restriping, or reducing the queue 

length through the techniques mentioned below.

Ramp metering technology has developed various methods of queue 

detection and corresponding solutions handled either by being hardwired into the controller or with the software as a function of the 

control algorithm. It is important to deploy a system that provides 

operators with information about the length of queue wait times. If 

adding additional storage capacity at a ramp is not feasible, the agency 

could consider adjusting the metering control scheme to increase ramp 

metering capacity. 

Strategies to increase ramp metering capacity include dual-lane or dualrelease metering, implementing the use of the ramp shoulder as a 

metered lane during peak periods or restriping the shoulder lane to 

allow for an optimal acceleration lane taper (see Figure 10 for a typical 

sign). These are lower-cost options for controlling the queue.

Because queue length is a crucial aspect of ramp metering operations 

that is relevant to many stakeholders, the agency should create policies 

on maximum queue wait time and be able to communicate and justify 

these policies publicly.

3.3 Operating Ramp Metering Effectively

Monitor performance

After deploying or expanding a ramp metering system, the agency 

should assess various dimensions of the system’s performance. It 

should establish which metrics to measure, appropriate benchmarks for 

those measures, and monitoring and reporting procedures.

Figure 10: Typical sign 

used to convert single 

lane on-ramp into duallane queue storage or 

allow conditional use of 

the shoulder
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 19

Performance monitoring can be used to identify 

areas of improvement and make small tweaks to 

the algorithm and overall system after the initial 

ramp metering deployment. Performance 

monitoring can also aid the agency in building 

inter-agency and public support for ramp 

metering. Creating public relations materials or 

reaching out to media regarding performance can 

increase the favorability of ramp metering with 

citizens, local businesses, and local governments.

Providing agency transparency on the effect ramp 

meters are having on the freeway network is a 

successful strategy to overcoming opposition and 

determining target areas for improvement.

Analyze costs and benefits

Measuring the costs and benefits of a proposed 

ramp metering system is a practiced strategy for accelerating ramp 

metering deployment. The agency could face scrutiny regarding the 

proposed benefits of ramp metering in its region. A benefit/cost

analysis can make the case for ramp metering more convincing. FHWA

has developed resources to assist in this analysis. The Intelligent 

Transportation Systems (ITS) Benefits database documents findings 

from evaluations of a variety of ITS deployments on system 

performance, categorizes benefits by ITS goal areas (such as customer 

satisfaction, mobility, safety), and provides a comprehensive summary 

of benefits that can help the agency in making informed planning and 

investment decisions. A companion to the Benefits database is the 

Costs database, a national resource of costs estimates for ITS 

deployments. The Tool for Operations Benefit/Cost (TOPS-BC) 

spreadsheet is designed to assist agencies in conducting benefit/cost 

analysis and to provide additional structure to critical decision-support 

actions and analysis of selected key TSM&O strategies. Another useful 

resource for analyzing impacts from ATDM strategies is the recent 

update to Chapter 35 of the Highway Capacity Manual (HCM), which 

describes methods to analyze freeway mainline effects of ATDM 

strategies, such as ramp metering. 

There are numerous costs associated with ramp metering, including 

capital and maintenance costs associated with hardware and 

installation, user costs, and other costs stemming from congestion, 

environmental pollutants, and safety. A sound evaluation of the benefits 

Figure 11: Dimensions of performance monitoring
20 October 2014

and associated costs of ramp metering can make a compelling case to 

relevant stakeholders that ramp metering would benefit a given area.

Monitor and manage ramp queues

Following the activation of ramp meters, the agency should give 

particular attention to the length and behavior of the ramp queues. 

As discussed, excessive ramp queues that back up onto arterials are 

hazardous from both an operational and public relations standpoint. A 

common criticism of ramp metering from the public is the time drivers 

must spend in queues, so maintaining support for ramp metering can be 

contingent on managing queues. In addition, drivers are more likely to 

comply with ramp meters when the 

queue is reasonable. The agency 

should establish policies and methods 

for regularly monitoring the ramp 

queues, as traffic conditions can 

change over time and throughout the 

day.

Through its data collection and 

analysis processes, the agency should 

make adjustments to algorithm 

parameters as needed. To 

accommodate various ramp 

dimensions, it may change the 

configuration of the ramp. This could 

include forming two-lanes during 

metering, lengthening the storage 

lane, and adding a full-time lane. The 

release policy could also be increased 

to two cars per green, which would 

allow cars into the mainline at a 

higher rate.

Figure 12 distills the keys presented 

above into mitigation strategies for 

common barriers to ramp metering.

Figure 12: Ramp metering deployment challenges and mitigation 

strategies
Ramp Metering: A Proven, Cost-Effective Operational Strategy | A Primer 21

SPOTLIGHT

WSDOT: Automated turn 

on/off

In November of 2012, WSDOT 

automated the on/off operation 

of the Seattle area ramp meters 

through an added function to the 

Fuzzy Logic algorithm that looks 

at traffic conditions local and 

downstream of the ramp. All 

meters have the ability to be 

automated and most of them are.

The few that are not automated 

are still in manual because of 

presence of construction activity.

ODOT: Adaptive ramp 

metering 

Oregon Department of 

Transportation (ODOT) switched 

its ramp meters from pre-timed 

operation to the SWARM

algorithm in 2005 to provide 

increased efficiency and 

effectiveness of a trafficresponsive ramp metering 

algorithm. About 150 ramps in 

the Portland metropolitan area 

are under adaptive control during 

the morning and evening peak 

periods.

(See Table 2 for algorithm 

descriptions)

4. GOING ABOVE AND BEYOND

After deploying a basic ramp metering system, the operation of the 

system may benefit further from increased sophistication. The extent to 

which an agency can and should develop its ramp metering program

can vary greatly. The need for these enhancements can also vary 

greatly, from agency policy preferences to managing excess volume. 

One of the key attitudes that agencies with successful ramp metering 

programs embrace is the desire for continued improvement in ramp 

metering operations. Through ongoing performance monitoring and 

internal agency assessment, enhanced ramp metering strategies can be 

identified and planned for in future regional planning efforts. 

Operational enhancements can include policies that extend the use of 

ramp meter operation outside the peak hours and for special events and 

construction activities, special ramp treatments, adaptive ramp 

metering, and integrated freeway and arterial corridor management 

strategies.

Special ramp treatments include strategies that can improve traffic 

conditions, improve safety at the merge point, and provide driver 

incentives for specific modes of travel. For instance, to encourage 

carpooling and transit use, some ramps have HOV bypass lanes that 

allow HOV and transit vehicles to avoid delay by bypassing the ramp

queue and merging onto the freeway. 

Adaptive ramp metering is one application out of the suite of Active 

Transportation and Demand Management (ATDM) concepts that aims 

to control the rate of vehicles entering the freeway utilizing advanced 

technologies. Part of the ATDM (and TSM&O) philosophy includes 

monitoring the transportation system and taking steps to continuously 

improve its operation. In other words, it is important to actively manage 

each ramp metering system. Exploration of basic ramp metering 

approaches to meet freeway management goals and objectives is 

beneficial prior to implementing more advanced technologies and 

concepts.

Agencies can also focus on developing the systems aspect of ramp 

metering. For instance, adaptive ramp metering employs algorithms 

that change release rates based on the level of congestion on the 

mainline. This technique is effective for recurring and non-recurring 

congestion, since it can respond to mainline traffic conditions and 

on/off mainline flow in real time.
22 October 2014

Another enhancement to a ramp meter system may be the integration of 

the arterial signal system as part of a system-wide corridor management 

strategy. When operating independently of the ramp meter signals, the 

arterial signals may release too many cars onto the ramp, causing 

backup onto the arterial. If the two systems are integrated, backup 

could be reduced leading to safer and more efficient conditions.

These approaches tend to require high organizational capability and are 

not necessarily suitable for all ramp metering locations. As stated 

above, even agencies that already have ramp meters should assess both 

suitability and feasibility prior to expanding and improving their 

programs.

U.S. Department of Transportation

Federal Highway Administration

Office of Operations

1200 New Jersey Avenue, SE

Washington, DC 20590

www.ops.fhwa.dot.gov

October 2014

FHWA-HOP-14-020