Work Zone Mobility and Safety Program

Appendix A - Example Work Zone Impacts Assessment:
Virginia Department of Transportation I-495/U.S. Route 1 Interchange Reconstruction Project

Project Overview

The Woodrow Wilson Bridge (WWB) project, in the Commonwealth of Virginia and State of Maryland, is a 7.5 mile-long corridor located on I-95/495 (also referred to as the Capital Beltway) extending from MD 210 interchange in Maryland, over the Potomac River, to Telegraph Road in Virginia. The existing Woodrow Wilson Bridge carries more than three times the traffic that it was designed to handle. Daily miles-long backups occur on both sides of the bridge where eight-lanes merge down to six for the bridge crossing, and several adjacent interchanges feed into the bridge causing merge/weave issues. The WWB project consists of widening I-95/495 to 12 lanes at the bridge and reconstructing four interchanges, including the I-495/U.S. Route 1 interchange in Virginia. The example work zone impacts assessment discussed in this appendix focuses on the I-495/U.S. Route 1 Interchange Reconstruction project. More information and data related to the project can be found at

Figure A.1 presents a high-level map of the WWB project location and Figure A.2 presents a more detailed location map (including the I-495/U.S. Route 1 Interchange).

Figure A.1 High-Level WWB Project Location Map

Map of I-95 and I-495 showing the location of the project on I-95 and I-295 near Alexandria, Virginia

Figure A.2 Detailed Project Location Map
Map showing a detailed view of the I-495 and U.S. Route 1 interchange in Alexandria, Virginia

The I-495/U.S. Route 1 Interchange project involves complete reconstruction of the existing interchange to provide for increased capacity, better geometry, and improved safety. This involves:

  • Bridge replacement and widening of the I-95/I-495 mainline roadway section from 0.91 miles west of U.S. Route 1 to the west abutment of the Potomac River Bridge at Royal Street.
  • Replacement of all the ramp movements.
  • Ramp connections to future HOV lanes.
  • Ramp connection to Eisenhower Valley at Mill Road.
  • Intersection improvements.
  • Retaining and sound barrier walls.
  • An extensive ground improvement program.
  • Utility relocations, including electrical transmission tower relocation.

Work Zone Impacts Assessment Process Example

This section contains an overview of the components of the work zone impacts assessment process that were applied to the I-495/U.S. Route 1 Interchange project to date.


The Virginia Department of Transportation (VDOT) has a general policy related to construction work zone lane closures. Briefly:

  • Lane closures are not permitted during AM and PM peak hour periods, Monday through Friday.
  • One lane can be closed during non-peak hour periods Monday through Friday.
  • Multiple lanes can be closed during overnight and weekend periods.

This policy was revised and tailored to address specific local issues related to the I-495/U.S. Route 1 interchange due to the following considerations:

  • Extensive commuter traffic.
  • Heavy traffic during Friday afternoons related to travelers departing the area early for the weekend.
  • Recreational traffic related to events in Alexandria.
  • Heavy overnight commercial traffic.
  • Regional recreational traffic related to major/special events (e.g., Washington Redskins football games, stadium concerts).

VDOT's general policy related to construction work zone lane closures was revised to address the local environment of the I-495/U.S. Route 1 interchange. Some of the highlights include:

  • Lane closures are not permitted between 5:00 – 9:00 AM and 3:00 – 7:00 PM, Monday through Thursday.
  • Lane closures are not permitted between 5:00 – 9:00 AM and Noon – 10:30 PM on Fridays.
  • One lane can be closed between 9:00 AM – 3:00 PM and 7:00 – 10:30 PM, Monday through Thursday.
  • Multiple lanes can be closed between 10:30 PM – 5:00 AM, Sunday through Thursday.
  • Directional and total roadway closures are permitted between Midnight – 5:00 AM, Sunday through Thursday for up to 20-minutes.
  • Lane closures or traffic restrictions will not be permitted on Saturdays, Sundays, and holidays from noon the day before the holiday until noon the day after the holiday unless otherwise approved by the Engineer. When a holiday falls on a Friday, lane closures are not permitted from noon Thursday to noon Monday. When a holiday falls on a Monday, lane closures are not permitted from noon Friday to noon Tuesday.
  • Lane closures are not permitted on Washington Redskins game days or other special events as specified by the Engineer.
  • In case of emergency or accidents, the construction access lanes on the shoulder within the project or lane closure limits (Outer Loop Express) must be available for emergency vehicles.
  • A shoulder cutout area should be deployed for every continuous ¼-mile of shoulder closure to provide a place for disable vehicles, nominally 10 feet by 200 feet in size.

Construction at the I-495/U.S. Route 1 interchange is to be conducted concurrent with other WWB construction projects. As such, a WWB project-wide Lane Closure Policy was developed to address differences in Virginia and Maryland lane closure policies and practices for providing for the safe, orderly and efficient movement of traffic through adjacent work zones. The WWB Lane Closure Policy addresses:

  • Procedures for approval to implement a lane closure including a detailed request form to provide consistency among all contractors.
  • Advance notification requirements (by lane closure type).
  • Advance notification limits to avoid "blanket" lane closure approvals.
  • How to secure State Police support.
  • Requirements and points of contact for lane closures.
  • Lane closure restrictions.
  • Holiday schedule.

The overall policy and policy provisions were applied to the respective program delivery stages as follows:

  • Systems Planning – No work zone policy provisions were applied during the systems planning stage of the I-495/U.S. Route 1 project.
  • Project Development – Revisions to VDOT's lane closure policy as described above were adhered to during the design of final plans, specifications, and estimates development. Lane closure exceptions have been granted to allow for:
    • Emergency repairs.
    • Extensions to existing work zones due to unforeseen complications that prevented the completion of planned work.
    • Opportunities for contractors to perform operations that have minimal traffic impact during off peak hours.
  • Construction – The contractor has complied with and has not recommended changes to the work zone policy provisions above.
  • Performance Assessment – Work zone policy provisions have not been assessed to date.

Since the project is underway and will not be complete until 2008, feedback from the various stages is not available to develop recommendations.

Systems Planning

A Transportation Technical Report[1] was developed for the WWB Project that also addresses the I-495/U.S. Route 1 interchange project. The report is the definitive technical transportation planning and analysis document for the WWB project and is one of several technical reports that are part of the documentation for the WWB Environmental Impact Statement (EIS). The Transportation Technical Report provides substantive, extensive, and detailed transportation data including:

  • An Introduction section with details on the project location, description, history, purpose and the need for action.
  • Summary of findings.
  • An overview of the existing transportation system including details on policy context, land use and travel patterns, roadway network, operational conditions, truck travel, and existing transit services.
  • A detailed overview of alternatives including the development process, future travel demand and patterns, end-to-end alternatives and a description of the no-build and build alternatives.
  • An assessment of future conditions including land use and travel patterns, operational performance and project related arterials, safety and operational performance, toll collection and public transportation.

A screening-level work zone impact assessment was not specifically conducted to identify whether the I-495/U.S. Route 1 interchange constituted a "significant project". However, it would clearly be a significant project under any criteria developed or based on engineering judgment. In addition, specific work zone management strategies were not developed during the planning phase of the project.

The EIS sets forth 51-pages of construction impacts for the WWB project, many of which are related to the I-495/U.S. Route 1 interchange including:

  • General phasing plans for six types of construction activities were set forth for the I-495/U.S. Route 1 project. These include distinct phasing plans for:
    • Demolition, utility work and permits, earthwork and drainage, pile driving, and foundation construction.
    • Mobilization, demolition, utility work, earthwork and drainage, pile driving, and foundation construction.
    • Utility work and permits (if required), earthwork and drainage, pile driving, foundation construction, substructure construction and superstructure construction.
    • Shift traffic to new lanes, earthwork and drainage, pile driving, substructure construction, demolition of old lanes, and superstructure construction.
    • Utility work and permits (if required), earthwork and drainage, pile driving, substructure construction, and superstructure construction.
    • Superstructure construction, paving, signing and lighting and landscaping.
  • Construction staging areas.
  • Environmental impacts and potential mitigation measures, including traffic, socio-economic, air quality, noise, natural environment, and cultural resources. Mitigation measures set forth in the EIS were clearly labeled as "potential" mitigation measures. Some of the measures identified for construction traffic impact mitigation included:
    • Maintenance of traffic and construction sequencing will be planned and scheduled to minimize delay throughout the project area.
    • Six lanes of traffic will be maintained over the Potomac River throughout the construction period.
    • Access to businesses and residences affected by construction will be provided.
    • Rerouting of traffic may be necessary during the construction. Lane or ramp closures could create circuitous routes for emergency services, but access will be maintained to all areas.
    • Signs will be used as appropriate to provide notice of road closures, detours, and other pertinent information.
    • Local media will be notified appropriately in advance of construction related activities that could excessively inconvenience the community.
    • Signs will be posted in the project vicinity with a hotline phone number for questions.
    • During final design, a maintenance of traffic plan for both pedestrians and bicyclists will also be developed, based on consultation with local jurisdictions and organizations.

The WWB Project Record of Decision (ROD) specifically states the design development process for the WWB project (which includes the I-495/U.S. Route 1 interchange) shall meet 12 design goals to the maximum extent possible. Three of the 12 goals are construction related:

  • All practicable measures shall be taken to minimize the construction period of the project.
  • Construction impacts to historic and archeological resources shall be avoided or minimized to the extent possible. If possible, construction related traffic in the City of Alexandria would be routed away from residential areas via South Street to minimize construction related traffic through residential areas north of the project.
  • The project shall be designed to avoid all temporary and permanent impacts to a local cemetery.

In addition, the ROD sets forth the following commitments and considerations:

  • Federal, State, county and local jurisdictions and organizations will be involved in the review process for maintenance of traffic (MOT) plans.
  • Detailed maintenance or traffic plans will be developed for each individual contract that address vehicular, pedestrian and bicycle traffic.
  • Coordination with local jurisdictions, community groups and residents to further identify and evaluate potential construction activities and their effects (i.e., haul routes, dust control, etc.).
  • Use signs, as appropriate, to provide notice of road closures, detours, etc.
  • Post signs in the project area with the phone number of a hot line people can call about project-related activities.

Preliminary Engineering

The following materials were available at the outset of preliminary engineering development:

  • WWB Transportation Technical Report.
  • WWB Record of Decision.
  • A separate WWB Project Traffic Projections and Operational Analyses document published four years after the WWB Project Technical Transportation Report. This report reflects the use of updated traffic data and land use assumptions for the agreed upon design alternative.
  • Conceptual horizontal plan view roadway alignment drawings.
  • WWB Construction Contract Summary. A graphical depiction of the anticipated construction projects was developed to illustrate the physical limits of each project. Start dates, end dates, and critical path dates were also set forth. This tool enabled engineers to better understand design and construction issues related to individual projects (e.g., I-495/U.S. Route 1 interchange) and coordination issues related to other adjacent contracts.
  • WWB Project Master Schedule. The schedule sets forth start and finish dates for all construction contracts envisioned at the outset of the preliminary engineering phase of the project. The schedule was updated monthly.

The I-495/U.S. Route 1 project was not re-assessed, nor the overall WWB project. The sheer complexity and size of the I-495/U.S. Route 1 interchange were understood by all parties involved in the project.

Candidate construction approaches were not developed as part of the preliminary engineering phase of the project because the final roadway alignment was not set forth until the end of the preliminary engineering design phase.

One of initial efforts of the preliminary engineering phase of the project was to identify cost savings through value engineering (e.g., elimination of a ramp, revisions to roadway alignment that conceptually could result in construction costs savings and time reductions). Once this was completed, engineers then began the extensive and detailed efforts necessary to decide on the horizontal and vertical roadway alignment and identify other issues (e.g., right-of-way requirements, utility relocation requirements) that needed to be addressed. A preliminary engineering cost estimate was developed for comparing an engineering cost estimate to the available, budgeted funding for the project.

An actual assessment of whether the project was significant was not conducted for the I-495/U.S. Route 1 project, or for the WWB project. However, it was understood that the expansion and reconstruction of the I-495/U.S. Route 1 interchange was a significant project – whether by itself or as part of the larger WWB project.

The following work zone strategies were identified and examined in detail for their applicability to minimize construction impacts upon traffic flow:

  • Intelligent Transportation Systems (ITS) – ITS that was anticipated to be designed for the final roadway alignment was also sought to be designed and deployed to help in the management of traffic during construction.
  • Incident Management – Strategies that would enhance incident management during and after the construction of the Woodrow Wilson Bridge (WWB) project were examined.
  • Travel Demand Management (TDM)/Transit – Strategies that could divert traffic away from the WWB construction zone were examined. Public information was also addressed as part of TDM/transit strategy identification.
  • Local Street Operations – Strategies and improvements along major alternate routes to be used by traffic diverting from the WWB construction zone to facilitate local travel during construction and times of incidents were examined.

ITS, incident management, TDM/transit, public information, and local street operations strategies that were identified as being cost effective and practical were recommended for approval and inclusion in the 30% preliminary project cost estimate. Only selected ITS, incident management and public information strategies were included in the 30% preliminary cost estimate as the TDM/transit and local street operations strategies were found not to be cost effective or practical.

It was also agreed that the deployment of the incident management and public information programs would be managed by the General Engineering Consultant (GEC). Program elements were not specific to the I-495/U.S. Route 1 interchange; rather, they were WWB project-wide. Having the GEC manage these programs would also enable a deployment of specific actions and activities that could be matched against anticipated spikes in corridor-wide work zone lane and/or ramp closure impacts.


In addition to the aforementioned Transportation Technical Report, Record of Decision and other materials (e.g., WWB Traffic Projections and Operational Analysis), the following materials were available and gathered at the outset of final engineering design development:

  • 30% preliminary engineering plans and cost estimate.
  • Additional traffic characteristics (e.g., volume, turning movements) used to aid in the preliminary engineering plan development.
  • Updated WWB Construction Contract Summary.
  • Updated WWB Project Master Schedule.

Multiple candidate construction staging approaches were developed for the I-495/U.S. Route 1 interchange contract, concurrent with taking the 30% preliminary design plans to the semi-final design stage. The management strategies themselves were not reassessed.

Similar to the Preliminary Engineering Module, the expansion and reconstruction of the I-495/U.S. Route 1 interchange was understood to be a significant project. As such, work zone impacts were analyzed for each candidate construction staging approach to build the I-495/U.S. Route 1 interchange including:

  • Detailed traffic engineering analyses were conducted to assess the traffic operations impacts related to closing shoulders, lanes, ramps, traffic switches, and queues.
  • The ability to respond, clear and manage incidents was reviewed with an emphasis on providing an incident management friendly work zone.
  • Opportunities to advance the deployment of permanent ITS field devices (e.g., closed-circuit television (CCTV) cameras, highway advisory radio (HAR), and dynamic message signs (DMS)) for use in supporting maintaining traffic flow through the construction zone were examined.

Coupled with this quantitative and qualitative analysis, working session meetings were held to review the various approaches with an emphasis on reviewing:

  • Constructability.
  • Feasibility.
  • Budget impacts.
  • Community impacts.
  • Environmental impacts.

A series of iterative working session meetings and refinements to proposed construction staging ultimately led to the selection of a an agreed upon construction staging sequence and supporting traffic control plan for the I-495/U.S. Route 1 interchange.

A final construction staging and supporting traffic control plan was developed for the I-495/U.S. Route 1 interchange project. Drawings specifying construction staging and detailed signing, striping and placement of traffic control devices were developed and set forth in the final contract plans.

A separate ITS construction contract was developed to advance the deployment of selected CCTV camera and DMS. The purpose for the break-out was twofold – to complete installation in advance of major interchange construction and traffic impacts, and to obtain the services of an ITS contractor in lieu of a general contractor. A special provision was developed and included in the final contract that required the contractor to submit site-specific traffic control plans for approval prior to the implementation of any work zones.

During the completion of the final design plans for the I-495/U.S. Route 1 Interchange, designers examined different methods to accelerate the duration of construction. Alternative maintenance of traffic plans were developed and CORSIM modeling software was used to further assess the traffic impacts of the alternate MOT plans. At this time, the contractor has not implemented these alternate MOT plans.


An I-495/U.S. Route 1 Construction Project Kick-off Meeting was held with key personnel including the contractor, Virginia DOT staff, the construction management and inspection team, and local utility agencies. Elected officials and representatives of local and county agencies were also invited to attend. Contract plans, construction staging, the traffic control plan and the WWB Project Lane Closure Policy were reviewed in detail. No alternative approach was proposed by the I-495/U.S. Route 1 interchange contractor. Thus, the anticipated work zone impacts reassessment was not conducted.

Through the first year of construction, construction staging and traffic control have been implemented by the general contractor as set forth in the final contract plans. Partnering meetings, held bi-weekly, have resulted in recommended substantive changes to construction staging and traffic control. The Contractor proposed the closure of a one-block stretch of a local street that would facilitate the installation of numerous utilities, traffic signal and a TMS conduit system that would require numerous lane closures for several months. The contractor's reasoning behind this proposal was they would go in and do the work, close the road one time, and have a viable detour route that would not send motorists to far from the existing route.

As a result of this proposal, a Synchro model analysis was conducted to analyze the implications of the disruption to motorist traveling through the work zone area. The result of the modeling indicated numerous improvements in traffic flow with no delays to motorists. Field observation demonstrated that the results of the analysis were consistent with how traffic was flowing through the work zone. As such, the recommended change was implemented.

With respect to work zone safety and mobility impacts monitoring during construction, the General Engineering Consultant team:

  • Conducts windshield surveys to review construction signing and striping installations for proper use and placement.
  • Conducts windshield surveys to monitor average queue lengths within and approaching the construction zone.
  • Conducts quarterly meetings, or meetings as needed with the State, county and local agency incident management community to review operations and advise them in advance of major construction changes.
  • Conducts an evaluation of traffic signal timing to insure signals are operating efficiently and effectively.
  • Has a dedicated staff person responsible for monitoring work zones with the use of CCTV at the project office.
  • Has a dedicated staff person responsible for updating real-time work zone information by utilizing highway advisory radio system.
  • Has dedicated staff responsible for addressing questions and issues raised by the local business and residential communities.
  • Coordinates lane closures and other operational issues with other nearby major roadway reconstruction projects.
  • Has work zone safety and mobility as a standing item for construction Partnering meetings.

A project web site was established for the overall WWB project ( This site contains information on:

  • The overall WWB project.
  • "Bridge Bucks" which provides a $50 incentive for using alternative modes of transportation.
  • "Mission Possible, Keep You Moving" program providing traveler information on:
    • Commuter solutions.
    • Employer solutions.
    • Current traffic conditions (real-time traffic, lane closures, traveler information).
    • Regional travel solutions.
    • Clearing traffic incidents.
    • Bridge openings.
    • Mariner's alerts.
  • Construction program (including the I-495/U.S. Route 1 Interchange project).
  • Project news.
  • Neighborhood news.
  • Environmental aspects.
  • Civil rights/DBE programs.
  • Project scrapbook.
  • Project videos.

Media releases similar to that shown in Figure A.3 are used to provide information to motorists on lane closure updates, major traffic changes, detours, etc.

Figure A.3 Sample News/Media Release from WWB Project Web Site
Sample news release stating that ramps in Alexandria, Virginia, are temporarily closed, requiring the use of detours

In March 2005, information about the project construction periods (phases) and the anticipated traffic impacts for 2005-06 was made available in a presentation that can be viewed on the project web site ( The presentation includes Figure A.4, which shows the work that was scheduled to occur during various construction periods for the I-495/U.S. 1 project.

Figure A.4 Anticipated I-495/U.S. 1 Traffic Impacts 2005–06
Map of I-495 and U.S. Route 1 interchange showing 12 areas of traffic impacts from winter 2005 to summer 2007

The presentation also contains several color-coded maps showing the anticipated U.S. 1 traffic impacts for the different construction periods, with a focus on impacts to the City of Alexandria. In the maps, the traffic impacts are classified into several levels:

  • Improvement - decrease in delays/travel times expected; opening new ramp/roadway; improved shoulders.
  • Low - slight increase in delays/travel times expected; lower speed, narrow or temporary ramp; slight lane shift, new temporary traffic signal.
  • Moderate - modest increase in delays/travel times expected; considerable lane shift; new merge point with minimal acceleration lane.
  • Severe - substantial increase in delays/travel times expected; significant lane shift.

Mitigation measures suggested for addressing these work zone safety and mobility impacts include:

  • Sequencing construction activities.
  • Reducing speeds to 50 mph in the project corridor.
  • Enhancing signs and pavement markings for clear and positive guidance.
  • Increasing police presence.
  • Coordinating activities with City of Alexandria traffic (signal timing, etc.).
  • Using CCTV cameras.
  • Disseminating real-time traffic information via HAR, overhead and portable VMS, project web site, and e-mail list.
  • Disseminating information about scheduled traffic changes (e.g., lane closure schedules) via telephone hotline, project web site, and media/stakeholder outlets.

During construction, work zone performance has been monitored through field observations and work zone evaluations.

Performance Assessment

The I-495/U.S. Route 1 Interchange project was under construction during development of this document. This step has not yet been conducted.

  1. USDOT Federal Highway Administration, Region 3, Virginia Department of Transportation, Maryland Department of Transportation, State Highway Administration, District of Columbia Department of Public Works, "Woodrow Wilson Bridge Improvement Study Transportation Technical Report," January 1996.

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