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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:

  • FHWA Resource Center (RC): Serves as both a partner of the RC and as a “resource” for the RC. Collaborates on IHSDM and HSM technical assistance and training.
  • FHWA Office of Safety (HSA): Supports HSA’s DDSA initiative and receives HSA support on IHSDM outreach activities (e.g., workshops and webinars).
  • FHWA Federal Lands Highway (FLH): Supports FLH’s application of HSM methods and/or IHSDM.
  • FHWA Safety R&D: Supports a range of in-house research efforts led by Safety R&D staff, and collaborates with other Safety R&D Lab/focus areas.
  • FHWA Division Offices: Coordinates with division offices in responding to technical assistance requests from State agencies.
  • AASHTO Safety: Provides technical support to HSM users via requests received through AASHTO; and investigates potential errors in AASHTO’s HSM.
  • State DOTs: Provides significant support to State DOTs and their consultants in understanding and implementing quantitative safety analysis via the HSM and supporting tools such as IHSDM.
  • Local DOTs: Assists local DOTs and MPOs in conducting safety analyses in data-limited environments.

In serving as a bridge between researchers and practitioners, the GDL supports the implementation of research that has already been completed, helps to ensure that research will be usable, and identifies research that should be done to help practitioners.

Laboratory Description

GDL staff focuses on the following tasks.

  • Research: Supporting IHSDM, Highway Safety Manual, and other highway safety-and geometric design-related research efforts. The GDL serves a variety of roles related to highway safety and design research, with varying levels of involvement in research activities. GDL research activities can thus be classified into the following categories:
  1. Conducting research directly.
  2. Identifying and advising FHWA of knowledge gaps and research needs.
  3. Providing input to FHWA on research being conducted by others.
  4. Providing technical input to researchers (e.g., HSM Part C model developers) to support the practical application of research results.
  5. Documenting existing applications of research and challenges of implementing new techniques/methods.
  • Technology Facilitation: Supporting technology facilitation for the IHSDM and HSM. The GDL plays a significant role as the primary source for IHSDM- and HSM-related technology transfer and technical support, including transferring accumulated technical knowledge to support IHSDM and HSM users, and the FHWA Resource Center; giving presentations at a wide range of venues; developing/maintaining content for the FHWA IHSDM website.  The GDL also markets IHSDM and HSM to decisionmakers and potential end users, assists efforts to develop and deliver IHSDM- and HSM-focused training/workshops, 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  and HSM-related initiatives 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 and the HSM for evaluating the safety of roadway designs. By combining transportation engineering and software development expertise, the GDL has the unique ability to evaluate safety analysis tools 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.

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

  • Coordinates the IHSDM User Group and the IHSDM Steering Committee.
  • Facilitates IHSDM/HSM-related webinars and meetings.
  • For all IHSDM safety evaluation modules (Crash Prediction, Design Consistency, Intersection Review, Policy Review, Traffic Analysis and Driver/Vehicle), the GDL conducted software testing to verify, validate, and evaluate the IHSDM software system and developed and/or finalized the software’s functional specifications.
  • Supports the FHWA Resource Center’s efforts to develop and deliver IHSDM training.
  • Provides the primary source of technical assistance to IHSDM users (; 202–493–3407).
  • Develops, reviews, maintains, and enhances documentation for IHSDM users.
  • Provides technical support in the development, production, and dissemination of IHSDM-related marketing materials.
  • Provides technical content for the FHWA 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.