“We know that the highway safety problem is made up of several factors, and unquestionably ‘what the driver sees’ along the road has an influence on the safe use of the highway facility.”

– Thomas H. MacDonald, Commissioner, U.S. Public Roads Administration, 1940

Whether a historic road is managed by the federal government, or a tribe, state or local agency (or a combination thereof), the historic road will interface with a number of transportation policies, regulations and standards. Some are rigid and inflexible (and may be a source of great frustration) while others offer tremendous flexibility and a range of allowable options. To prevent frustration, it is imperative that preservation advocates, and the state and tribal preservation offices (SHPOs and THPOs) that may have authority to comment on projects proposed for historic roads listed in or determined eligible for National Register (or tribal, state and locally designated historic sites), understand where options exist, where the transportation agency has discretion and where time-tested standards and proven methods present little opportunity for change. Remember, transportation policy is based on safety, so any options or flexibilities proposed for a historic road must maintain or enhance existing safety levels.

Safety & Liability

Carriage Drive, Acadia National Park, Maine. Credit: Paul Daniel Marriott


For many historic roads, constructed to earlier standards and different needs, the provision of a safe driving environment for the modern traveler requires special considerations. The unique design and history of most historic roads makes the standard application of modern safety features and devices without a comprehensive safety study both unwise and potentially unsafe. All too often historic features (walls, bridges, trees) are removed or seriously altered due to a concern that such features may pose a hazard or as the result of an accident. In many instances such changes are made based on the fact that the features are of a design or in a location that would not be considered appropriate by today’s design and safety standards. Yet seldom do such actions include a comprehensive analysis identifying the full complement of features and factors that may generate an unsafe situation.

A safety plan should look at the historic road holistically. Accident statistics should be compared to the geometrics (horizontal and vertical alignment, sight distance and superelevation) and existing safety features (barriers, walls, traffic signals, shoulders). Consider, for example, automobiles striking a historic bridge balustrade—is the historic barrier a safety concern, or did a road-widening approaching the bridge increase the exposure to the balustrade? Only with a thorough understanding of the current safety functioning of the historic road can an assessment be made to determine if historic features enhance or harm the safety of the motoring public.

Consult your local, state or federal land highway engineering office to determine features of your historic road that may be problematic, even dangerous. Before you are too quick to write off everything of the past, however, look carefully at how your road functions today. It is possible some of those old details may be functioning as effective safety devices even though that was never their design intent. Cobblestone pavement, for example, may be an effective tool for traffic calming (speed reduction).

There may be attributes of a historic road that will require modification or alteration for modern safety, use or environmental needs or requirements. Reconciling modern needs with historic roads can be difficult, but is seldom impossible. In addition to an engineering analysis, a safety study should also address the safety implications of historic roadside features (street trees, access drives, lighting, rock outcrops or balustrades). Only after completing such an analysis can historic road advocates and the managing organization make a wise assessment of the potential impact such additions or alterations may have on the historic road.


Concerns for liability (the legal responsibility a managing agency holds for a particular road or transportation system) direct many of the decisions on the design and management of our national highway network. All road managing agencies or owners, through local, state, tribal or federal law are required to provide a safe driving environment, or sufficiently warn a motorist of a potentially unsafe situation. Tort liability is a situation in which an injury or harm has occurred, due to a breach of a preexisting duty (providing a safe road), resulting in the potential exposure for damages to be awarded to the injured party or parties.

Every tribal, state and local jurisdiction addresses liability differently. In some states liability cases against the government are limited, in others departments, even individuals, may be held directly accountable for an accident resulting on a roadway. Additionally, the assignment of responsibility in a tort liability situation may be interpreted differently by different courts.

When investigating the potential liability risk a historic road may pose, it is helpful to review the safety history of the road. In addition to physical elements that may have resulted in an accident (structures, barriers, trees, walls), it is also important to investigate driver behavior (under the influence of drugs or alcohol, seizure, poor eyesight, aggressive driving) and environmental conditions (poor weather, ice, distractions due to a billboard, missing signs or improperly functioning traffic signals). Try to determine larger patterns such as repeated accidents at particular locations or particular times of day and determine if past efforts to improve safety at accident sites have succeeded in reducing the number of accidents, or if such efforts have “shifted” accident locations.

To minimize the risks associated with liability and safety, accommodations and additions to historic roads should be well documented. Crash tests, alternate constructions or flexible designs should be provided as part of a written record citing the safety rationale for the selected design.

The following issues, features or concepts may be addressed in a safety and liability analysis:

engineering design: Most of the fundamental safety components of any road are established in the overall engineering design. The geometrics of a road—its calculated and measured movement through the landscape—are defined by its alignment and cross section. These, combined, determine both the design speed (the maximum safe speed for which the road is designed) and the posted speed (the maximum legal speed identified—generally lower than the design speed). Alignment is defined as both horizontal (movement to the left or right—a road’s curves) and vertical (movement up or down—the road’s hills or grades). Alignment is a principal determination of site distance (how far ahead the driver has a view of the pavement, a desired attribute—hills or curves limiting site distance, for example). Cross section elements include the width of lanes and shoulders, slope or crown and superelevation (the “banking” of curves on higher speed roads).

Modern engineering concepts, if thoughtfully and appropriately applied to a historic road can greatly enhance safety with a minimal negative visual impact—the addition of superelevation to make a high speed curve safer, for example. Engineering design analysis may also assist in understanding the functioning of a historic road—demonstrating a road’s curves have a posted speed that exceeds the recommended design speed based on their geometry.

speed: Modern design advances have enabled today’s automobiles to travel at average speeds well above those when many of our historic roads were constructed. Modern highway design with broad curves and superelevation further facilitates high speed driving. Accidents that occur at higher rates of speed are more likely to result in fatalities. Most traffic experts agree that reducing the posted speed, as an action to reduce speed, is generally ineffective—drivers will not arbitrarily lower their speed due to a new posting, and enforcement, spotty at worst and expensive at best, can never be guaranteed twenty-four hours-a-day (raising a liability concern).

traffic calming: Traffic calming, a movement that began in Europe to reduce traffic speeds, has been widely implemented in the United States. As a principle, traffic calming introduces physical changes (speed humps, chicanes or “channels,” traffic circles or narrower lanes) to force a reduction in motorist speeds. While successful in reducing speeds on many roads throughout the country, the physical changes introduced through traffic calming may compromise the integrity of a historic road. Many historic roads, however, by their design, embody elements of traffic calming. When looking at the safety of a historic road, consider the possibility that original lane widths, narrow bridges and winding curves may be keeping speeds lower. It is also possible that the restoration or rehabilitation of historic cobblestone or brick pavements, due to their rough texture and audible tone, may aid in reducing or maintaining lower speeds.

 expectancy: Expectancy is a safety concept based on driver behavior and responses to changes in the roadway environment. Essentially, it suggests that when a driver is presented with a consistent, reliable and predictable driving experience, he or she will respond prudently and appropriately. Thus both fifty miles of a narrow twisting mountain road and fifty miles of interstate highway equally establish an expectancy that drivers instinctively respond to—caution and slower speeds on the mountain road compared to high speeds and confidence on the interstate. Safety problems tend to occur where an established expectancy is altered—a sharp curve or an entry ramp without an acceleration lane on an interstate highway, or a short segment of a wide, straight road in the middle of the narrow winding mountain route (possibly sending the instinctive “signal” to motorists to increase their speed).

barriers and walls: Barriers and walls (guardrails, wire cables, wood posts, boulders and stone constructions) protect the automobile occupants from roadside hazards (fixed obstacles such as trees or bridge piers, or topographic dangers such as cliffs or ditches) and errant vehicles (an automobile crossing a median). Many historic barriers and walls, while constructed to the advanced engineering standards of their day, do not meet current guidelines for safety. Additionally, many of the locations that today require a barrier or wall may not have had such installations historically. To improve safety without compromising historic integrity, a number of states and the federal government have redesigned historic barriers to meet modern crash testing requirements while maintaining the historic “look” of the original barrier. Design requirements for barriers and walls are based on the speed of the road, and can vary significantly.

pedestrian and bicycle safety: The majority of our national safety policies are geared toward the occupants of motor vehicles. Yet pedestrian and bicycle fatalities have approached twenty-percent of our annual traffic-related fatalities during some years (National Transportation Safety Administration). For historic roads associated with parks and recreation, urban thoroughfares or rural Main Streets, a pedestrian and bicycle presence is part of the contemporary, and often historic, use. For these types of historic roads, it is important to consider the impacts safety improvements will have on both the motor vehicle occupant and the pedestrian or bicyclist.

Highway Standards & Policies

The AASHTO Green Book

Most state and local safety policies are based on the guidance recommended by the American Association of State Highway and Transportation Officials (AASHTO)—generally referred to by its popular name pronounced “ASH-tow”.

The AASHTO guidance for highway design, A Policy on Geometric Design of Highways and Streets, is known most popularly as the Green Book. The purpose of the Green Book is to recommend safe and efficient practices for the design of roadways. The recommendations contained in the Green Book are based on extensive research and study, and generally provide a range of acceptable design criteria based on the type of roadway and the expected traffic volume for the facility. The FHWA has adopted the Green Book as the minimum standard for projects on the National Highway System (NHS), which includes the Interstate System and other selected principal routes and connectors to intermodal facilities (check with your state transportation department to see if your historic road is a part of the NHS). For all other projects, developed with Federal-aid funds or not, design is directed by the standards adopted by the state or local government. Almost every state and the majority of local governments have adopted the Green Book in whole or in part for use on their own projects. Remember the guidelines and recommendations contained in the Green Book do not become “standards” until adopted by your state or local government.

When working with the Green Book, it is important to remember the flexibility contained in the range of criteria recommended. As noted, this flexibility is at the discretion of your state or local transportation department. It should also be noted, under special circumstances, that solutions outside the recommended range may be sanctioned by the FHWA for projects on the NHS. This special approval, known as a “design exception,” is based on a clearly articulated need and demonstration that the proposed solution will not lead to a safety problem.

Section 4(f)

Section 4(f) of the Department of Transportation Act of 1966, 49 U.S.C. § 303, is a substantive requirement that prohibits federal approval or funding of any transportation project that requires the “use” of any historic site, public park, recreation area, or wildlife refuge unless there is “no feasible and prudent alternative to the project,” and “all possible planning to minimize harm to the project” has been addressed (DOT Act, 1966, Sec 4[f]). The use of Section 4(f), long a powerful tool for the preservation of historic roads, was modified in 2005 so that it may be fulfilled in certain situations by the Section 106 process. If there is a finding of “no adverse effect” under Section 106, even with a minor use of an historic property and the SHPO concurs, there is no further requirement for a 4(f) evaluation. An adverse effect finding, on the other hand, requires the agency to seek options/flexibilities for the preservation of an affected historic property, including a historic road (or other historic resources) negatively impacted by a federally funded highway project. In other words, where 106 and 4(f) were once invoked concurrently, 4(f) is now applied only if the Section 106 process results in an adverse effect to the historic property in question. Section 106 is the first course of action for historic properties impacted by federally funded transportation projects.

Advocacy Organizations

Advocacy organizations were one of the critical forces behind the development of our modern highway network. Through boosterism, research, planning and political action during the Good Roads era, these organizations served an important role in defining need, design and use.

Today, both formal and informal advocacy organizations are being formed and planned around our nation’s historic roads. Some serve as recorders of history and popular culture, while others are actively involved with the design and management of historic facilities. If properly developed and organized, they may become credible and respected partners providing valuable assistance to the management entity.

An advocacy organization can record, research and document a road’s history; assist the managing organization in reporting safety problems, vandalism, and maintenance issues; and serve as an independent “watchdog” organization to ensure that state and federal policies and reviews are being upheld. Naturally, advocacy organizations are the principal generator and organizer of community outreach through special or commemorative events, public awareness projects, community publications, scholarly research and interpretive programs. Depending on the structure of the advocacy organization and its relationship with the managing agency, advocacy organizations can also lobby, campaign or fundraise on behalf of the historic road, or provide volunteer labor for clean-up projects, traffic surveys and restoration projects. For longer historic routes and corridors, they may serve as a unifying voice for multi-state or regional historic roads.


As historic roads are increasingly recognized as unique resources deserving of special management considerations and administrative accommodation, a number of states have issued policy statements that direct transportation departments to undertake specific actions or activities related to a historic road or roads. Policy statements carry legislative authority and require legal actions that can greatly assist in the proper analysis and management of a historic road. The following represent a wide range of policy statements and management strategies for historic roads.

Connecticut: Policy for the Merritt Parkway (1994)[PDF of Policy Statement| Coming Soon]

Hawaii: A Bill to Support Flexible Design on Hawaii’s Roads (2006)[PDF of Policy Statement | Coming Soon]

New Jersey: Historic Roads Inventory[PDF of Policy Statement | Coming Soon]

Oregon: State Policy to Preserve the Historic Columbia River Highway (1995)[PDF of Policy Statement | Coming Soon]

Traffic congestion, between 1915 and 1925, Detroit, Michigan. Credit: Library of Congress