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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations

This report is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-HRT-04-091
Date: August 2004

Signalized Intersections: Informational Guide

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5.1  Project initiation

5.2  Identify Stakeholder Interests and Objectives

5.2.1 Intersection Users

5.2.2 Adjacent Property/Business owners

5.2.3 Facility Managers

5.2.4 Other Decisionmakers

5.3  Data Collection

5.3.1 Office Review

5.3.2 Field Investigation

5.4  Problem Identification

5.4.1 Establish Performance Measures and Criteria

5.4.2 Summarize Operational and Safety Conditions

5.4.3 Develop Problem Statement

5.5 Identify Problem Cause

5.6 Treatment Selection

5.6.1 Identify Range of Treatments

5.6.2  Evaluate treatments.

5.6.3  Assess Potential To Introduce Undesirable Effects

5.6.4  Determine Costs and Implementation issues

5.7 In-Service Assessments

5.7.1 Followup Plan

5.7.2 Monitoring program



Example stakeholder interests and objectives

User characteristics
Operational characteristics
Safety characteristics
Geometric, traffic signal control, and land use characteristics
Policy and background information
Common concerns raised by stakeholders
Example performance measures and criteria
Possible causes of intersection problems

5. 0   Project Process

This chapter describes a standard process for conducting an intersection design/redesign project. During the initial stages of a project, stakeholders are identified, the scope of analysis is determined, data are collected, and key issues of concern are identified. From this information, a problem statement is developed and potential countermeasures or treatments are identified. In the alternatives evaluation stage, potential treatments are evaluated for feasibility and effectiveness. After a treatment is chosen, the improvement is implemented and monitored over time. This chapter describes a general thought process to guide readers to issues to consider and questions to ask.

5.1 Project initiation

An intersection project typically begins with notification to a lead engineer. The engineer could be a city, county, or State traffic engineer responding to a concern raised by the public, a supervisor, a planning commission, or a city council. In other cases, the lead engineer may be a consultant responding to a request for proposal for a particular intersection design project. During this process, the lead engineer should gather initial information that will lead to identification of problems. Information should be gathered through stakeholder interviews, review of existing data, and field visits as described in the following sections.

Two questions that should be asked at the outset of the process are:

  1. Does the project involve a new or existing intersection?

  2. Does the intersection experience system-wide effects?

New intersections typically afford greater flexibility for design and the selection of treatments than do existing ones. Existing intersections are often constrained by utility placement, presence of development surrounding the intersection, and issues related to construction and to maintenance of traffic. The effect of a treatment at an existing location must take into account the effect on user expectancy. Changes to way-finding, lane geometry, and traffic control may result in confusion and, in turn, create a safety deficiency.

Determining whether an intersection condition is part of a system problem is an important consideration when evaluating intersection treatments. For certain cases, a capacity improvement to an intersection may provide little benefit if the constraining point on the system is located upstream or downstream of the intersection. Likewise, implementing an improvement such as a turn movement restriction may solve an operational or safety problem at the subject intersection, but may result in the migration of the problem to a new location. These system effects must be considered at each step in the treatment evaluation and selection process.

5.2 Identify Stakeholder interests and objectives

Each project should begin by identifying the affected stakeholders and conducting stakeholder interviews to define interests, goals, and objectives. Stakeholders include any person or group affected by a project: users of the facility (motorists, pedestrians, bicyclists, etc.); adjacent property owners and residents; jurisdictional owners and managers of the facility; and decisionmakers who have influence over making improvements to the facility.

The interest range of stakeholders is widespread: A local business owner may be solely concerned with maintaining access for his/her business; a neighborhood group may want pedestrian treatments to improve the safety for a pedestrian crossing; and a traffic engineer may want to maximize throughput on the mainline facility. a planning commission may recommend yet another treatment based on concerns raised from its constituents.

It is important to highlight the interests of all stakeholders and clearly define their goals and objectives early in the process. This includes defining jurisdictional policies and standards regarding the safety and operations of the intersection. Stakeholders’ goals and objectives need to be considered carefully and acknowledged at each step of the process, and should be tied to performance measures to provide a means for evaluation.

The following sections identify usual stakeholders and provide direction to readers for highlighting the interests, goals, and objectives for each.

5.2.1 Intersection Users

Intersection users include motorists, pedestrians, bicyclists, and transit riders (see chapter 2 for a more complete discussion of user types). These users may be categorized in subgroups with similar concerns and issues (e.g., citizens from a neighborhood group, disabled persons, truck drivers).

It is important to understand how the goals and objectives of each user group relate to each other, and the tradeoffs that exist between them. For example, lane-widening improvements that are implemented to solve an operational deficiency for motorists may reduce the safety and quality of service for pedestrians due to the number of conflicts added and the increased crossing distance. In some cases, the benefits experienced by one user group may be offset by the negative impacts imposed on another.

5.2.2 Adjacent Property/Business owners

The access and circulation needs for adjacent properties and business owners should be addressed based on an evaluation of the land use, traffic demand, and access needs of each site. Air quality and noise impacts to adjacent properties and businesses are also important consideration when evaluating improvement alternatives.

5.2.3 Facility Managers

Stakeholders include the owners and managers of the facility such as state departments of transportation engineers and city and county planning and public works staff. Facility managers typically are expected to meet an adopted standard or policy for the facility. As part of the stakeholder identification process, relevant and adopted documents such as state highway plans, comprehensive plans, and transportation system plans should be reviewed to identify the transportation standards and policies in place that may affect the study intersection. In addition, jurisdiction officials should be contacted and interviewed to identify plans for system improvement that may affect the characteristics or demand patterns at an intersection.

5.2.4 Other Decisionmakers

It is also important to consider other decisionmakers in addition to local jurisdiction officials, including technical advisory committee members, steering committee members, planning commissioners, city councilors, and other government officials. It is important to gain an understanding of the criteria that each of these decisionmakers uses in evaluating recommendations and making decisions. Driving forces may include local policy, local politics, agencies/organizations represented, and level of ownership and commitment to the project.

A summary of the key concerns and issues of each stakeholder should be prepared and circulated to relevant project team members to ensure that everyone has a clear understanding of the constraining factors of a project. Table 19 provides an example of cataloging stakeholder interests and objectives.

Table 19. Example stakeholder interests and objectives.


Primary interest



Mobility, ease of commute

Coordinated signal system–limited stop-and-go conditions


Mobility and safety

Fewer conflicts, reduced crossing distance, direct connections, adequate facilities


Mobility and safety

Provision of bike lane, minimized conflicts with motor vehicles, extended clearance interval

State traffic Engineer

Mobility on State highway

Maximize throughput on mainline

City Planner

Long-term operations

Obtain necessary right-of-way and funding to construct improvements sufficient through a 20-year horizon to accommodate all modes

City Engineer


Minimize severity and frequency of crashes

Neighborhood Group

Pedestrian/bicycle access

Provide bike/pedestrian connections linking residential area with shopping district

Business owner


Maintain full-access turn movements at driveways

Planning Commissioner

Compliance with local standards and policies

Ensure intersection meets operations standards and intent of policy for safety, accessibility, and pedestrian/bicyclist/transit usability

5.3 Data Collection

Data acquisition and field investigation provides an understanding of the physical and operational characteristics of the study intersection and identify factors that contribute to its deficiencies. All information required for analysis and evaluation should be obtained in this step. The amount and type of data required for analysis is dependent upon the analysis method selected. Additional site visits may be required after the initial visit to obtain supplementary data. A description of the analysis methods available for safety and operational evaluation, along with specific data requirements, are described in chapters 6 and 7. The following sections describe the data that should be collected and obtained for an office review and field investigation.

5.3.1 Office Review

Office reviews include obtaining relevant safety, operations, and design data from available resources (e.g., local public works and planning departments, State department of transportation offices, and Internet sites). As-built drawings and aerial photography should be obtained for this effort. Past studies conducted within the study area should also be obtained. In general, the office review should make use of all data that can be obtained without extraordinary expenditures.

5.3.2 Field Investigation

Field investigations should be performed to observe safety and operating conditions. Everyone involved with evaluating and recommending improvements to an intersection should visit the site. Three perspectives should be considered.

  1. User perspective: visibility, ability to process information, decisionmaking, level of service, and conflicts for all user types.

  2. Intersection perspective: operations and safety performance, geometric characteristics, movements operating with high delay/overcapacity, safety conflicts, signal timing, signing, and pavement markings.

  3. System perspective: impacts of upstream/downstream intersections, influence of adjacent driveways, location relative to other facility types.

The site visit should occur during peak-hour traffic conditions. Additional field visits may be appropriate for the following conditions:

  • Off-peak periods.
  • Night.
  • Inclement weather.
  • Special events.
Observations of events and physical characteristics should be noted. Photographs and video should be made for reference and use in presentations and reports.

During the observation, vehicle queues and travel patterns through the intersection should be examined and noted if they interfere with upstream driveways and/or intersections. Likewise, arrival patterns, modal distribution, operations, and closely spaced downstream traffic signals should be observed to determine if they affect, or are affected by, operations at the subject intersection. Special conditions such as nearby pedestrian/bicyclist generators, transit transfer points, and populations with special needs should be noted. The type and operating characteristics of nearby commercial establishments and institutions may have an important effect on the intersection and should also be noted. The intersection’s relationship to other important system components (e.g., freeways, principal arterials, and even sensitive neighborhoods) must be recognized.  To assess the system-wide impacts of a potential improvement, it is necessary to understand how the study intersection interacts with its surrounding facilities.

The following tables provide a description of the data items that should be collected as part of the office review and field investigation stages. Table 20 identifies user characteristics, table 21 identifies operational characteristics, and table 22 identifies safety characteristics. Table 23 identifies physical characteristics such as geometry, traffic signal control, and land use, and table 24 lists key policy and background information that should be obtained.

5.4 Problem Identification

Problems at an intersection are identified through a synthesis of stakeholder interviews, office reviews, field investigations, and preliminary operational and safety analysis. To determine whether a problem exists, this information needs to be evaluated against defined goals or standards. a problem statement can be defined after a review of the established operational and safety criteria against the known characteristics of an intersection. In some cases, additional data may need to be collected to confirm that a problem exists.

The steps for identifying problems as described in this chapter are: (1) establish performance measures and criteria; (2) summarize operational and safety conditions; and (3) develop a problem statement.

Table 20.  User characteristics.

Data Item



Motor vehicle traffic volumes

Includes ADT volumes for a roadway segment and peak-hour turning-movement volumes for existing and future year conditions

Travel patterns, high-demand (critical) movements, appropriate number of lanes for a roadway approach

Origin-destination information

Detailed description of vehicle movements classified by start and end points

Expected lane utilization, whether a weaving condition is expected, impact a turn movement restriction may have on surrounding area

Heavy vehicle data

Identification of number and type of trucks, percentage of trucks by movement

Appropriate design vehicle for geometric evaluation, whether special consideration is warranted to account for heavy vehicle movements

Pedestrian and bicyclist demand

Volume and/or demand and location of pedestrian and bicyclist movements as well as location of nearby generators and attractors

The level of activity that needs to be accounted for in the design and signal timing of an intersection

Table 21. Operational characteristics.

Data Item



Capacity analysis

Evaluation of traffic operations for either a planning level, macroscopic, or microscopic level analysis (see chapter 7 for details on performing an operational analysis)

Critical movements, volume-to-capacity ratio, average intersection delay, level of service, vehicle queues, pedestrian capacity and level of service, bicycle capacity and level of service

Delay study

Measure time each vehicle (car, truck, transit, or bicycle) enters and discharges from queue; measure time each pedestrian arrives and departs; measure available gaps in the traffic stream for pedestrians to cross

Average delay per vehicle by approach, average pedestrian delay, average bicycle delay, average transit delay

Saturation flow study

Measure time headway for vehicles discharging from a stopped position

Average saturation headway and loss time per approach

Queue observations

Identify location of maximum back of queue and number of vehicles in queue

Required storage lengths, whether queues interfere with upstream driveways or intersections

Vehicle speeds

Identification of 85th percentile speeds and posted speeds for all approaches

Whether a speeding condition exists, signal design parameters

Table 22. Safety characteristics.

Data Item



Crash history

Includes summary of reported crashes for past 3 to 5 years

Whether excessive crashes are occurring when compared to crash data for similar facilities

Conflict study

Identification of conflicts and near-collisions

Potential for collisions

Collision diagram

Diagram illustrating location, type, and severity of reported collisions

Whether a pattern in crashes exists

Interview with local police and jurisdiction officials

Identification of anecdotal evidence regarding crash history of intersection

History and background of an intersection’s safety condition

Table 23.  Geometric, traffic signal control, and land use characteristics.

Data Item



Lane configuration

Number of lanes on approach, lane use type (shared vs. exclusive), presence of add/drop lanes, free-flow movements, storage lengths for turn bays, and distance to nearby driveways and intersections

Presence of weaving sections, adjacent driveways/ intersections within influence of intersection, presence of short lanes

Pedestrian facilities

Location and configuration of crosswalks, ramps, accessible treatments, pedestrian signal equipment, and network connectivity

Pedestrian crossing distance, compliance with ADA requirements, traffic signal needs

Bicycle facilities

Location and configuration of bicycle lanes, detection equipment, and network connectivity

Bicycle facility needs, traffic signal needs

Roadway/ intersection geometric data

Cross slopes, channelization features, posted and prevailing speeds, lane widths, right-of-way locations, median type, horizontal and vertical curve data, corner radii, presence of bicycle/pedestrian/transit facilities, sight distance, and presence of offsets/skews

Whether physical constraints exist; right-of-way available to accommodate improvements; presence of horizontal or vertical curves that may affect sight distance and speeds

Illumination drawings

Location, type, and wattage of street lighting

Whether lighting is adequate

Roadside features

Location and type of roadside elements including drainage ditches, trees, shrubs, buildings, signs, street lights, signal poles, etc.

Whether roadside elements may be leading to fixed-object crashes, sight distance deficiencies, or driver confusion

Traffic signal phasing and timing plans

Type of signal control (actuated or pre-timed), coordinated/noncoordinated operations, cycle length, left-turn phasing type, phase order, and timing parameters (loss time, clearance intervals, min/max greens, unit extension, etc.)

Whether intersection is located in a coordinated system; whether left-turn phasing treatments such as permissive or protected-permissive may be a cause of collisions

Adjacent land uses

Size and type of use, location and type of driveways, circulation patterns, design vehicles

Access needs for local land uses

Table 24. Policy and background information.

Data Item



Planned developments and transportation improvements in the area

Location, site, type, and completion date of planned and approved developments; description of improvement project, limits of project, and scheduled construction dates

Additional traffic volumes that may affect facility; impacts to travel patterns that can be expected from an improvement project

Functional classification of roadways

Description of facility type for intersecting roadways

System-wide function of intersecting roadways

Design standards

Standards for lane widths, medians, curb radii, sidewalks, bike lanes, curb ramps, signal timing, etc.

Requirements for intersection design; may indicate that design modifications are needed

Applicable plans and studies

All applicable access management plans, corridor studies, transportation system plans, traffic impact studies, bicycle and pedestrian plans, ADA transition plan, etc.

Existing and projected future safety/operational characteristics of intersection

5.4.1 Establish Performance Measures and Criteria

The selection of performance measures should be made on a case-by-case basis; the measures should address concerns raised by stakeholders and issues identified during the office review and field investigation. Table 25 lists common concerns of motorists, pedestrians, transit riders, bicyclists, and facility managers.

Table 25.  Common concerns raised by stakeholders.



Transit Riders/Operators


Facility Managers

  • Takes more than one signal cycle to get through intersection
  • High delays
  • Queue spillback
  • Too many stops
  • Inefficient signal timing
  • Too many crashes
  • High severity of crashes
  • Poor sight distance
  • Vehicle speeds too high
  • Confusing signing
  • Inadequate facilities
  • Wait time too long
  • Crossing distance too far
  • Vehicle speeds too fast
  • Ramps and/or pushbuttons poorly located
  • Too many conflicts
  • Inability to identify when to begin crossing
  • Bus stop inaccessible
  • Bus stop impedes vehicle movement
  • Bus stop poorly located for pedestrians to use
  • Difficult for bus to merge into traffic stream
  • Facilities not adequate
  • Clearance interval too short
  • Lane striping ineffective
  • Unsafe/too many conflicts with vehicles
  • Local/Statewide policy not met
  • Not in compliance with comprehensive plan, transportation system plan, corridor plan, etc.
  • Construction impacts and maintenance of traffic during construction
  • Fiscal, land use, and right-of-way constraints

Ideally, performance measures are quantitative and can be measured for a future-year condition to evaluate the long-term effects of potential treatments. Certain cases, however, may require selection of qualitative performance measures, particularly when evaluating characteristics such as driver expectations and pedestrian/bicyclist comfort.

Once performance measures are defined that adequately address the scope of the issues, desired performance levels should be established for each measure. This process should take into account local policy and standards, driver expectations, operational and safety levels at similar facilities, and research findings. All decisionmakers on a project should agree on the performance levels established.

Desired levels of performance should be defined for all study periods and years. For operational evaluations, the typical weekday peak hour(s) should be included in the evaluation. Other conditions may be included as deemed necessary. Operational performance levels should be established for year of opening and long-term (20 to 25 years) conditions. For safety evaluations, performance levels are generally established on an annual basis and evaluated over a period of 3 to 5 years.

The desired performance level may vary based on time of day and year. For an operational issue, a degraded level of performance may be tolerated for certain periods of the day while more stringent standards are applied for the remaining periods. Similarly, a worsened operating condition may be tolerated better under long-term conditions than near-term conditions.

In some cases, particularly for multimodal aspects, it may be difficult to establish quantifiable performance levels. Performance levels for these cases may be based on a design element (e.g., sidewalk width, buffer, distance to transit stop). Efforts should be made to establish quantifiable levels to effectively assess the impact of various treatments.

A list of example performance measures and criteria is provided in table 26. Numerical values in the performance level column were developed for a hypothetical example.

Table 26. Example performance measures and criteria.

Performance Measure

Concerns addressed

Desired Performance Level
(What is acceptable?)

Critical movement volume-to-Capacity Ratio

Motorist operations

0.90 (peak 15 minute period for 5-year condition); 1.00 (peak hourly period for 20-year condition)

Average Vehicle Delay

Motorist operations

55 seconds or less per vehicle (to achieve level of service (LOS) D or better)

Vehicle Queues

Motorist operations and safety

Eliminate queue spillback

Total Intersection Crashes

Motorist safety

Reduce existing crashes by 20%

Crash Severity

Motorist safety

Reduce fatal and injury crashes by 20%

Approach Speeds

Motorist, bicyclist, and pedestrian safety

Reduce 85th percentile prevailing speed by 16 km/h (10 mph)

Pedestrian Delay

Pedestrian operations

40 seconds or less per pedestrian (to achieve LOS D or better)

Pedestrian accessibility

Pedestrian usability

Compliance with ADA standards

Total bicycle Conflicts

Bicycle safety

Reduce number of bicycle-motor vehicle conflict points by 25%

Transit Delay

Transit operations

Reduce transit vehicle delay by 10%


Motorist, bicyclist, and pedestrian operations and safety

Reduce intersection clutter, increase conspicuity of key road signs and signal heads, provide accessible routes for pedestrians

As shown in table 26, certain performance measures are readily quantifiable (critical movement volume-to-capacity ratio, average vehicle delay, queues), while others have a higher level of uncertainty for prediction (total intersection crashes, approach speeds) or require a qualitative assessment (multimodal impacts and way-finding). While some measures are not easily quantifiable, it is important that they be recognized and considered in the evaluation and selection of intersection treatments.

5.4.2 Summarize Operational and Safety Conditions

Problems at an intersection usually are related to a safety or operational deficiency. Defining a problem generally requires an assessment of performance from the perspective of all users of the intersection, regardless of mode of travel. At this stage in the project, a primary problem may have already been defined and be the cause for initiating the project. In these instances, the operations and safety conditions should be reviewed to confirm the problem exists and determine whether other problems exist or likely will exist in the future.

The level of effort required for determining operational and safety conditions at this stage varies from intersection to intersection. The information gathered through the stakeholder interviews and office review/field investigation may be sufficient in some cases, while other situations may require more extensive operational and safety evaluations.

Common questions that should be answered in evaluating intersection safety and operations are:

  • Is sight distance adequate?

  • Are red light running violations occurring?

  • Does the intersection have enough capacity under existing and future conditions?

  • Are pedestrian and bicycle facilities available, adequate, and supportive of existing or potential use?

  • Is adequate queue storage available to accommodate all turn movements?

  • Do signs and pavement markings clearly and accurately communicate the intended message?

  • Do upstream or downstream intersections interfere with operations at the subject intersection?

  • Are nearby driveways interfering with intersection operations?

  • Is there a pattern of collision type or location?

  • Are crashes occurring under inclement weather or nighttime conditions?

A complete description of analysis procedures that can be applied to estimate safety and operations conditions for signalized intersections and answer the above questions is provided in chapters 6 and 7.

5.4.3 Develop Problem Statement

After comparing the operational and safety conditions of an intersection against the established performance measures, problems and deficiencies should begin to emerge. Deficiencies should be expressed in terms of the user group (motorist, pedestrian, bicyclist, etc.) and reference the specific movement that initiates the problem as well as the time and duration during which the problem occurs. For example, a safety condition could be expressed as: an excessive number of rear-end collisions involve vehicles traveling on the northbound approach during wet-weather conditions. An operational problem could be stated as: an eastbound left-turn movement operates over capacity during the weekday p.m. and Saturday peak periods.

Problems should be stated in terms of the performance measures defined earlier in this chapter.  Example problem statements follow.

  • Excessive conflict for one or more movements.

  • Excessive number of collisions or type of collision.

  • Excessive number of injury/fatal collisions.

  • Inadequate capacity for one or more movements.

  • Excessive vehicle delay for one or more movements.

  • Excessive vehicle queuing for one or more movements.

  • Inaccessible pedestrian facilities.

  • Excessive pedestrian crossing delay.

  • Excessive transit delay.

  • Excessive number of bicycle-motor vehicle conflicts.

5.5 Identify Problem Cause

Once the problems at an intersection have been identified, initiative should be taken to determine the cause of each. The previous section explained that the effect of a problem is often a deficient safety or operational performance measure. The cause of the problem, in many cases, is attributable to a design element. As an example, a safety problem with an effect of a high occurrence of sideswipe collisions on an approach with dual left-turn lanes may be caused by inadequate lane width and a lack of delineation for the left-turn lanes.

Aerial photography and as-built drawings should be used to assist in the determination of problem cause. Results from the office review, field investigation, and preliminary analysis should also be used to determine possible causes. Detailed review of all elements of a signalized intersection, as described in previous chapters, are required to determine the cause of a problem.

Table 27 provides lists possible causes related to common operational and safety deficiencies. This list should be applied to specific movements and approaches where an operational or safety deficiency may be occurring.

Table 27.  Possible causes of intersection problems.

Potential Cause




Injury/Fatality Collisions

Effects from nearby intersections

check mark

check mark

check mark

check mark

Insufficient number of through lanes

check mark

check mark

check mark

check mark

Insufficient design or lack of turn lanes

check mark

check mark

check mark

check mark

Insufficient pedestrian crosswalk, ramps, landing area, and accessible facilities

check mark

check mark

check mark

check mark

Insufficient bicycle detection

check mark


check mark

check mark

Speed differential

check mark

check mark

Poor pavement conditions

check mark

check mark

Turning movements from adjacent driveways (poor access management)

check mark

check mark

check mark

check mark

Poor sight distance

check mark

check mark

Poor signal visibility

check mark

check mark

Inadequate signal phasing and/or timing (including vehicle and pedestrian clearance intervals)

check mark

check mark

check mark

check mark

Poor dilemma zone protection

check mark

check mark

Inadequate roadway lighting

check mark

check mark

Inadequate roadway signing

check mark

check mark

Inadequate pavement marking

check mark

check mark

Bicycle conflicts

check mark

check mark

check mark

Pedestrian conflicts

check mark

check mark

check mark

Bus conflicts

check mark

check mark

check mark

check mark

5.6 Treatment Selection

Treatments should be selected that address the specific areas for safety and operational improvement identified in the preceding stages of the intersection evaluation process. The primary objectives of the treatment selection stage are to (1) identify the range of treatments; (2) evaluate treatments; (3) assess potential for undesirable effects; and (4) determine costs and implementation issues.

5.6.1 Identify Range of Treatments

What treatments are likely to influence the areas for safety and operations improvement? The range of treatments provided in this guide are categorized into the following chapters:

  • System-wide treatments (chapter 8).

  • Intersection-wide treatments (chapter 9).

  • Alternative intersection treatments (chapter 10).

  • Approach treatments (chapter 11).

  • Individual movement treatments (chapter 12).

A list of identified treatments is provided in chapter 1. A complete discussion of the safety, operational, and design characteristics of each treatment is provided in part III of this guide, which also discusses the applicability of each treatment and identifies the problem and cause the treatment addresses. The level of detail provided for each treatment varies based on the amount of research and field evaluation available. It should be noted that treatments listed in this guide by no means represent the full extent of treatment possibilities.

5.6.2 Evaluate treatments

Once possible treatments have been listed that could address the identified problems, it is necessary to evaluate the possible countermeasures to determine the potential for improvement to safety and operations. Treatment descriptions in part III describe the impact each treatment has on safety and operations. Where available, crash modification factors are provided to estimate the possible reduction in crashes. Operational benefits can be determined based on performing an analysis described in chapter 7.

5.6.3 Assess Potential To Introduce Undesirable Effects

In addition to considering the potential safety and operational improvements that countermeasures can offer, consideration needs to be given to the possibility that countermeasures can have negative effects. Efforts should be made to assess the likelihood of introducing undesirable safety or operational consequences through the implementation of recommended countermeasures. These undesirable effects include the potential for a treatment to result in:

  • Out-of-direction travel.

  • Increased speed.

  • Cut-through traffic.

  • Illegal maneuvers.

  • Driver confusion.

  • False expectations.

  • Adverse impacts to pedestrians, cyclists, and transit users.

  • Migration of a safety or operational condition to another location.

5.6.4 Determine Costs and Implementation issues

Costs are usually assessed in three categories: capital costs, operating costs, and maintenance costs. Other issues that should be considered include right-of-way needs, ADA compliance, environmental impacts, constructability, and maintenance of traffic.

Capital costs are normally associated with initial construction and implementation. The installation of traffic signals, for example, involves design, materials, construction, and installation costs normally paid for out of a capital program fund. This is normally a one-time cost. Where the capital investment is projected to occur some time in the future (e.g., grade separation 10 years from now), these costs must be discounted back to present value to enable a fair comparison with other alternatives.
  • Operating costs are usually associated with consumables. In the case of traffic signals, the principle operating expense is electrical power for signal operation and illumination.

  • Maintenance costs are periodic, recurring costs of keeping an initial investment productive. For traffic signals this may include the time and materials associated with monitoring, periodic retiming, replacing lamps, repairing malfunctions in timing and operation, and repairing and replacing damaged equipment.

  • The amount of right-of-way required and the ability of the local agency to acquire needed property may influence the decision to implement a treatment.

  • Treatments must also be evaluated to determine their potential impact on drainage, wetlands, historic landmarks, and archaeological features.

  • The construction of a treatment may have a significant impact on the existing flow of vehicular and pedestrian traffic. Constructability issues and maintenance of traffic for each mode should be considered in the treatment evaluation stage.

The final decision to implement treatments should incorporate a wide range of parameters that decisionmakers deem appropriate. While operational benefits, safety benefits, and cost are key criteria, they are not the only elements that must be considered. Other criteria, such as coordination with other projects, special funding, and ADA transition plan requirements, may dictate the implementation and timing of a project.

5.7 In-Service Assessments

5.7.1 Followup Plan

Identifying and documenting the physical and operational hazards determined during the safety assessment should be coupled with a followup plan. The plan should identify what measures will be taken by whom and when, and it should effectively communicate these decisions to each of the stakeholder groups identified above.

The objective of a followup plan is to ensure that the:

  • Department, jurisdiction and/or agency responsible for implementing the proposed countermeasures is properly notified of the action required.

  • Period to implement these countermeasures is properly conveyed, including urgency.

  • Remedial measures, when completed, are done in accord with best practices, have addressed the hazard, and have not created unforeseen negative impacts on traffic operations or safety at the location.

Where the action of others is required to achieve the implementation of a recommendation, an appropriate followup system should be implemented. The system should endeavor to do more than simply monitor the status of other activities. If recommendations involve the need for design, those involved in the intersection evaluation process can use the followup process to comment on design and installation details before the remedial measures and countermeasures are ultimately installed. Staff familiar with the original intent of these measures should also ensure that the proposed measure was installed as directed.

5.7.2 Monitoring program

A monitoring program should be developed to evaluate the impacts of countermeasures that are selected and implemented. The scope of the monitoring program will be a function of the nature of the countermeasures and their likely effects on operations and safety at and adjacent to the study location. Ideally, data would be collected prior to construction of a treatment to provide a benchmark for future comparisons. The objectives of the monitoring program are to:

  • Focus on the dominant collision types to determine whether the recommended countermeasure has improved the performance at the specific location by causing a decline in the dominant collision types.

  • Focus on the dominant operational deficiency to determine whether the recommended countermeasure has improved the performance at the specific location by reducing the delay and queuing experienced by motorists.

  • Identify effects on all users.

  • Ensure that the recommended treatment does not adversely affect safety or operations on the road network.

  • Improve techniques and practices for identifying existing or potential operational concerns.

  • Provide data that can be used in establishing quantitative safety measures, such as crash modification factors, for the road authority.

  • Justify improvements to the road authority’s transportation-related standards, policies, and procedures that are applied in all areas from transportation planning to roadway and right-of-way maintenance.

The monitoring program should have a clearly understood monitoring frequency, duration, and objectives, as appropriate for the measure installed. The need to advise stakeholders of the monitoring program should be considered, but may not always be necessary. However, should the monitoring program result in a modification or removal of the originally proposed countermeasures, further notification to the stakeholders is required.

A key goal of the program is to be able to continually improve the road system, constantly seeking to reduce the number of collisions that occur on roads within the jurisdiction and improve the operational efficiency.

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Turner-Fairbank Highway Research Center | 6300 Georgetown Pike | McLean, VA | 22101