In April 2023, commuters on the George Washington Memorial Parkway (GWMP)—also known as the G.W. Parkway—might have wondered what the construction was about. During that time—in the Washington, D.C., metropolitan area—the National Park Service (NPS) began implementing changes and slowing traffic on the northern portion of the parkway. NPS and the Federal Highway Administration have collaborated since 1926 through interagency agreements and now through the Federal Lands Transportation Program to provide road design and construction assistance. The NPS Federal Lands Transportation Program uses transportation industry standards and performance-based, data-driven decisions to maintain and modernize its transportation system.

Part of this construction project, scheduled for completion in late 2025, is sponsored by NPS along with FHWA’s Eastern Federal Lands Highway Division (EFLHD), with the aid of the Turner-Fairbank Highway Research Center’s Office of Safety and Operations Research and Development, and the Federal Outdoor Impact Laboratory. The goal is to improve the safety performance of the parkway’s park road and roadside hardware without sacrificing its aesthetic effect.

“It is vital for us and our NPS partners to preserve the historic look and feel of the parkway while implementing safety measures that will protect the traveling public now and for years to come,” says Monique Evans, director of EFLHD. “The safety provisions used on the GWMP project are an example of balancing these very important priorities.”

Missions and Visions

The NPS missions for the park road include:

• Providing access to scenic or historic areas in a manner that complements its environment by preserving the natural or scenic character of its roads.
• Accommodating larger volumes of traffic at higher speeds than conceived when it opened in 1962, as many NPS roads have become important links  in growing metropolitan areas
• Meeting safety and aesthetic goals through enhanced designs for roadside safety hardware.

To achieve these missions, traffic barriers—beyond those commonly used on most public roads (e.g., the standard galvanized steel W-beam or concrete safety shape barrier)—are required. Park roads use aesthetic barriers such as stone-faced walls and steel-backed timber guardrails. Aesthetic barriers, however, have not all been developed or tested to the latest industry crash testing guidelines of the American Association of State Highway and Transportation Officials Manual for Assessing Safety Hardware (MASH). GWMP’s construction project offers the opportunity to ensure these types of aesthetic barriers, widely used on roads under the jurisdiction of NPS, meet the MASH industry crash test criteria. MASH is an industry standard and not required by Federal law.

The mission of FHWA is to deliver a world-class system that advances safe, efficient, equitable, and sustainable mobility choices for all while strengthening the Nation’s economy. Safety is the cumulative result of efforts in many different sectors, with roadside safety hardware representing a key aspect. Roadside safety hardware is part of the highway infrastructure that functions to reduce run-off-the-road crash severity and includes signs, guardrails, and other types of safety devices. For example, traffic barriers play a key role by containing and redirecting vehicles, keeping vehicles from leaving the traveled way, and preventing vehicles from encroaching on objects on the roadside. With NPS’s aesthetic objective and mission to provide access in a manner that preserves the natural or scenic character of its roads, standard traffic barriers may be inconsistent for projects like GWMP. “FHWA has and continues to promote standards for designing, deploying, operating, and maintaining the many roadside safety hardware elements,” says Brian Cronin, program director of the U.S. Department of Transportation’s Intelligent Transportation Systems Joint Program Office. “The George Washington Memorial Parkway project is an excellent example of transportation agency partners working together to create safer, more resilient roadway systems.”

Designing Roadside Hardware Through the Use of Crash Simulation

Over time, State and Federal transportation agencies have identified effective alternatives to traditional traffic barriers and developed both safety standards and protocols to assess them. The means to evaluate these alternatives, physically and analytically, have also evolved significantly. The process used in this project involves the development and use of finite-element (FE) computer models of vehicles and barriers to simulate the impacts of a vehicle with the barrier. Computer crash simulation—a numerical technique for solving mathematical problems that represent a destructive crash test of a car or a barrier system—analyzes the response of both the vehicle and barrier when an impact occurs and investigates factors such as stresses, deformations, fractures, and other effects on each part of the vehicle and barrier resulting from the impact. These analyses subdivide each part into smaller sections called elements, which might best be thought of as many small cubes characterizing the item. The impact forces are distributed across all the cubes, and the forces are distributed by the properties of each cube and those adjacent to it. These simulations have been shown to be extremely accurate representations of the effects of a collision. For the GWMP project, following proper research and simulation techniques ensures roadside hardware design practices are used to develop, upgrade, or modify its barrier systems.

Crash simulation and modeling have evolved and proven to be a powerful means to analyze safety issues and develop new and improved highway barriers and other roadside hardware concepts, which can lead to MASH-compliant roadside hardware, confirmed by crash testing. FHWA believes its initiatives to develop the fundamental tools necessary for roadside hardware crash simulations have led to safer roads. The initiative includes the development of detailed FE models of vehicles and barriers, as well as funding efforts to use FE tools to address emerging safety issues from changes in the vehicle fleet (such as higher weights and physical dimensions) to changes in safety hardware. Considerable knowledge is gained from crash simulation in a faster time, and at a lower cost, providing a sound basis for enhancing the safety performance of vehicles and roadside hardware.

The Impact of Crash Simulation on GWMP

Crash simulation technology was developed more than 40 years ago and has often become the first aspect in efforts to design and analyze the safety of new barrier concepts. Validations of the process over the years have shown a high degree of reliability in tracing crash effects as well as replicating the overall result by comparing them to full-scale crash testing. Simulation rapidly allows designs to be varied, and a range of impact angles, speeds, barrier designs, and vehicles to be considered. Crash simulation helps transportation researchers and designers to revisit older roadside hardware designs, such as the ones used by NPS, and update them to meet the new industry crash test guidelines.

The computer simulation analyses performed in the GWMP project started with the original designs of these safety hardware systems, which were then modified and reanalyzed as needed to predict whether the final design would meet the appropriate MASH crash test level requirement. Roadside hardware is designed and examined for different test levels according to the road on which it will be generally used. For example, a Test Level 3 (TL-3) design would typically be used on a high-speed or high-volume roadway or both, such as a freeway. In the GWMP effort, once simulations were completed, full-scale MASH crash tests of each design proposed for use on the GWMP were conducted using a pickup truck and a small car, as indicated by the MASH industry crash test criteria. These final tests confirmed that the developed designs meet all MASH criteria for TL-3 crash tests.

Eduardo Arispe, as a member of the Roadway Safety Team within FHWA’s Office of Safety and Operations Research and Development, works on finite element modeling and crash testing of roadside hardware to improve safety. He earned an M.S. degree in transportation safety engineering from The George Washington University and a B.S. in chemical engineering with a specialization in systems and controls from the University of Maryland.

For more information, see https://highways.dot.gov/research/laboratories/federal-outdoor-impact-laboratory/federal-outdoor-impact-laboratory-overview, or contact Eduardo Arispe, 202-493-3291, eduardo.arispe@dot.gov.