Work Zone Impacts Assessment

This Guide is designed to help transportation agencies develop and/or update their own procedures for assessing and managing the work zone impacts of their road projects throughout the different program delivery stages. Understanding work zone impacts is critical to developing effective work zone transportation management plans (TMPs) that provide for safety, mobility, and quality in maintaining, rehabilitating, and rebuilding the nation's highways. The primary intended audience for this Guide is transportation agency staff, including technical staff (planners, designers, construction/traffic engineers, highway/safety engineers, etc.); management and executive-level staff responsible for setting policy and program direction; field staff responsible for building projects and managing work zones; and staff responsible for assessing performance in these areas. This document also provides support to agencies in their efforts to implement the recently updated work zone regulations. In September 2004, the FHWA published updates to the work zone regulations at 23 CFR 630 Subpart J. The updated rule is referred to as the Work Zone Safety and Mobility Rule (Rule) and applies to all State and local governments that receive Federal-aid highway funding. Transportation agencies are required to comply with the provisions of the Rule by October 12, 2007. The changes made to the regulations broaden the former Rule to better address the work zone issues of today and the future. The Rule provides a decision-making framework that facilitates comprehensive consideration of the broader safety and mobility impacts of work zones across project development stages, and the adoption of additional strategies that help manage these impacts during project implementation. The Rule requires agencies to develop an agency-level work zone safety and mobility policy to support systematic consideration and management of work zone impacts across all stages of project development. Based on the policy, agencies will develop processes and procedures to support implementation of the policy. These include procedures that address work zone impacts assessment, work zone data, work zone training, and process reviews. The Rule also calls for the development of project-level procedures to help agencies assess and manage the work zone impacts of individual projects. While the Rule does not require a specific work zone impacts assessment process/procedure, it recommends that agencies develop and implement systematic procedures to assess work zone impacts in project development, and to manage safety and mobility during project implementation. This document is the last of four guidance documents developed on the Rule, and provides a general approach for conducting work zone impacts assessment and management, as well as many examples of the approaches currently being used by transportation agencies.

Road maintenance activities involve both short-term stationary work zones and moving work zones. Moving work zones typically involve striping, sweeping, pothole filling, shoulder repairs, and other quick maintenance activities. Existing traffic analysis tools for work zone scheduling are not designed to model moving work zones. A review of existing literature showed that many of the existing studies of moving bottlenecks are theoretical in nature, limited to certain lane configurations, and restrictive in the types of mobile work zone attributes considered. This research project sought to address this gap in existing knowledge by using field data from moving work zones to develop and calibrate a traffic impact analysis tool. This objective was accomplished through the fusion of multiple sources of work zone and traffic data. Four different data sources were used: Missouri Department of Transportation (MoDOT) electronic alerts (e-alerts), probe-based travel times, data from point detectors, and field videos of moving work zones recorded from the back of a truck-mounted attenuator (TMA). A linear regression model was developed to predict traffic speed inside a moving work zone. Predictor variables in the models included historical speed, number of lanes, type of lane closure, and time of day. The simulation tool VISSIM was calibrated for moving work zones using information extracted from videos of moving work zone operations. The three recommended calibration parameters are a safety reduction factor of 0.7, a minimum look ahead distance of 500 ft, and the use of a smooth closeup option. These calibration values can be used by departments of transportation (DOTs) to model moving work zone scenarios. The operational analysis concluded that a moving work activity lasting one hour or more operates best when traffic volumes are under 1,400 veh/hr/ln, and preferably under 1,000 veh/hr/ln. Further, scheduling shorter duration moving activities on high-volume roads at multiple times (on the same day or on different days) works better than scheduling a longer duration activity. The safety analysis generated tradeoff plots between the number of conflicts and combinations of activity duration and traffic volume. A DOT can use these plots to determine, for example, if it should conduct a moving work activity for a short duration when the volume is high or for a longer duration when the volume is lower.

Current Federal Regulations (23 CFR 630 Subpart J) encourage States to collect and analyze both safety and mobility data to support the initiation and enhancement of agency-level processes and procedures addressing work zone impacts. The purpose of this guidance document is to provide practitioners with the skills to identify current data sources (both existing data and data collected specifically for the work zone) for use in work zone performance measurement, as well as potential data sources that could be useful to work zone performance measurement in the near future. This document is also intended to assist practitioners in determining how to select and compute useful work zone performance measures, given the data sources available to them. For both current and potential data sources, guidance is presented on the viability of each source for work zone performance measurement, as well as on possibly leveraging opportunities to maximize the value of data collection and extraction efforts. In addition to information about data sources and opportunities, guidance is provided regarding work zone performance measures that the various data sources can support. Where appropriate, examples are provided as to how data assessment, collection, application, and interpretation can be accomplished. In this way, document users can obtain an overall perspective.

This guide was written as a quick primer for transportation professionals and analysts who assess the impacts of proposed transportation actions on communities. It outlines the community impact assessment process, highlights critical areas that must be examined, identifies basic tools and information sources, and stimulates the thought-process related to individual projects. In the past, the consequences of transportation investments on communities have often been ignored or introduced near the end of a planning process, reducing them to reactive considerations at best. The goals of this primer are to increase awareness of the effects of transportation actions on the human environment and emphasize that community impacts deserve serious attention in project planning and development-attention comparable to that given the natural environment. Finally, this guide is intended to provide some tips for facilitating public involvement in the decision making process.