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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Geometric Design Laboratory Overview


The mission of the Geometric Design Laboratory (GDL) is to support the Office of Safety Research and Development in research related to the geometric design of roadways and the impacts on safety. The GDL provides technical support to develop, maintain, and enhance tools for the safety evaluation of highway geometric design alternatives. This includes coordination of the Highway Safety Manual (HSM) with related tools, e.g., the Interactive Highway Safety Design Model (IHSDM). The GDL supports the HSM through implementation of HSM methods in IHSDM software; by providing technical support to HSM users; by performing HSM-related technology facilitation; and by conducting HSM-related training and research.

Those efforts also contribute to the Federal Highway Administration’s (FHWA’s) Roadway Safety Data Program (RSDP) initiatives to advance State and local safety data systems and safety data analyses.

The GDL supports the FHWA Safety Training and Analysis Center (STAC) in its mission to assist the research community and State departments of transportation (DOTs) in using data from the second Strategic Highway Research Program’s (SHRP2) Naturalistic Driving Study (NDS) and Roadway Information Database (RID).

Overall, the GDL’s focus can be described as the advancement of the safety practice. This comes in the form of conducting research which leads to usable information and tools; as well as providing technical support to researchers and practitioners to assist their efforts to develop and apply safety analysis methods and tools.

Many GDL activities fit under the broad category of Data-Driven Safety Analysis (DDSA) , which employs newer, evidence-based models that provide state and local agencies with the means to quantify safety impacts similar to the way they do other impacts such as environmental effects, traffic operations and pavement life. The GDL’s focus also includes and supports the general areas of performance-based analysis and design; performance effects of geometric design; and safety performance and analysis.

Historically, the GDL has served to bridge the gap between research and practice, for example by assisting agencies in developing and carrying out plans for conducting data-driven safety analysis at both the project and program level. Supporting DDSA/HSM implementation is a high priority for the GDL. Through a coordinating type of role, the GDL serves to connect a range of FHWA, and State and local offices. 

Laboratory Description

GDL staff focuses on the following tasks.

  • Research: Support IHSDM, Highway Safety Manual, and other highway safety-and geometric design-related research efforts.
  • Software Development: Support the full life cycle of IHSDM software development, including developing functional specifications; performing verification and validation of the models that are core IHSDM components; providing recommendations to the IHSDM software developer on all facets of the software (e.g., the graphical user interface, output/reporting); preparing IHSDM documentation; and performing alpha testing of IHSDM software.
  • Technology Facilitation: Support technology facilitation for the IHSDM and HSM. The GDL provides the primary source of technical support to IHSDM users and provides technical support to HSM users. GDL markets IHSDM and HSM to decisionmakers and potential end users, participates in developing and delivering IHSDM/HSM training, and coordinates the IHSDM User Group and IHSDM Steering Committee.

Laboratory Capabilities

The staff of the GDL includes professionals with expertise in transportation engineering and familiarity with software development, which allows the GDL to support IHSDM development in various ways and to assume a unique coordination role. The GDL’s transportation engineering expertise supports the laboratory’s function of reviewing and assisting the development of the engineering models included in IHSDM for evaluating the safety of roadway designs. By combining transportation engineering and software development expertise, the GDL has the unique ability to evaluate software from both the software developer and end-user perspective.

Communications and engineering skills help GDL staff to understand the needs of the audience (e.g., design engineers), thereby supporting effective technical assistance to end users.

IHSDM development is a long-term effort, involving research contractors, software developers, and FHWA staff. In addition, FHWA seeks input from end users and user organizations to help ensure that IHSDM is responsive to user needs. The staff of the GDL helps coordinate the interaction of all those involved with IHSDM development.

Staff at the GDL participates in HSM development and technology facilitation. In addition, the IHSDM Crash Prediction Module is a faithful implementation of HSM Part C (Predictive Method). Therefore, GDL staff is well equipped to support HSM-related activities.

Laboratory Equipment

The GDL is equipped with computer hardware and software typically employed by users of IHSDM and the HSM, including commercial CAD/roadway design software.

Laboratory Services

The GDL supports the HSM through implementation of HSM methods in IHSDM software; by providing technical support to HSM users; by performing HSM-related technology facilitation; and by conducting HSM-related research.

To develop and promote IHSDM, GDL staff provides or has provided the following services:

  • Coordinates the IHSDM User Group and the IHSDM Steering Committee.
  • For all IHSDM safety evaluation modules (Crash Prediction, Design Consistency, Intersection Review, Policy Review, Traffic Analysis and Driver/Vehicle), the GDL conducts software testing to verify, validate, and evaluate the IHSDM software system and develops and/or finalizes the software’s functional specifications.
  • Participates in development and delivery of IHSDM training.
  • Provides the sole source of technical assistance to IHSDM users (; 202–493–3407).
  • Supports coordination and integration of IHSDM with civil design software packages.
  • Develops, reviews, maintains, and enhances documentation for IHSDM users.
  • Conducts technical reviews and prepares review comments on contract research deliverables.
  • Provides technical support in the development, production, and dissemination of IHSDM-related marketing materials.
  • Provides technical content for the IHSDM Web site.

The GDL supports STAC in assisting the research community and State DOTs in using data from the SHRP2 NDS and RID; e.g., by assessing analytical possibilities associated with GIS data linkages to the RID.

Last updated: Monday, September 13, 2021