Summary of International Scanning Program for Highway Geometric Design

John Okamoto
NW Region Administrator
Washington DOT

The basic premise of a properly designed roadway is to consider the mobility and safety issues while addressing its physical and human environmental aspects. To achieve such a balance, trade-offs among these factors are needed which are routinely performed either consciously or subconsciously.

The passage of the Intermodal Surface Transportation Efficiency Act of 1991 emphasized the importance of such highway design. Practices that demonstrate such a design were compiled and documented in a report by the Federal Highway Administration (FHWA) titled "Flexibility in Highway Design." This document emphasized the existing flexibility in design guidelines and encouraged the use of creative design in addressing the needs of specific projects. This philosophy was coined in the U.S. as Context Sensitive Design (CSD) and represents an approach where a balance between safety and mobility needs within the community interests is sought.

Both FHWA and the American Association of State Highway and Transportation Officials (AASHTO) recognize the flexibility that exists in the current design guidelines, but at the same time they understand that the current focus on providing high levels of mobility often conflicts with the interests of the community. There is an increasing interest in CSD issues; research has been initiated to address them by the Transportation Research Board (TRB), and workshops have been developed sponsored by the FHWA. Moreover, there is a desire among the highway design community to improve the highway design practices and incorporate elements not currently used to enhance established practices.

The CSD approach is a current practice in several European countries which use several highway geometric design concepts and tools used to address design issues. Therefore, European agencies can offer the U.S. valuable new insights and concepts from their experience in these issues and practices. Such concepts can be transferred to the U.S. environment to enhance the knowledge base regarding CSD and highway geometric design.

Objectives and panel composition
The objective of this scanning tour was to review and document procedures and practices in several European countries. Sweden, Denmark, the Netherlands, the United Kingdom, and Germany were identified as countries which have innovative methods and procedures related to highway geometric design and project development. The goal of the tour was to identify practices in these countries that, when implemented in the United States, will enhance the current procedures and ensure highway designs that equally address mobility and community issues.

The Highway Geometric Design International Scanning Tour was jointly sponsored by FHWA and AASHTO, and the U.S. delegation was assembled by FHWA's International Technology Scanning Program. The delegation included members representing FHWA, AASHTO, state Departments of Transportation (DOT), the American Public Works Association (APWA), and academia. The delegation members offered expertise in many highway geometric design and project development issues, including context sensitive design practices and procedures, application and use of various parameters used in geometric design for enhancing traffic safety and enforcing speed moderation, and consideration and integration of bicyclists and pedestrians in highway design.

General conclusions
The U.S. delegation met with several representatives from transportation and highway ministries, research organizations, and consultants who shared many interesting ideas and insights regarding the scan tour topics. A summary of the practices the delegation found most significant follows.

Project planning
The countries visited have an underlying philosophy of a project planning process aiming to improve safety and reduce crashes, while being sensitive to the needs of the community and focusing on improving the existing system by making better use of it. A general conclusion from all countries visited was that the project development process is similar to that of the U.S. but is more clearly defined. Furthermore, there are several points where differences were noted. A major difference is that a longer period of time is devoted to the planning process, and longer sections, typically entire corridors, are considered. Such an approach provides the opportunity for long-range planning by allowing for a more systematic overview and definition of needs and deficiencies over the entire system.

Another difference in the process is the greater emphasis on urban areas and the efforts to better integrate projects in communities by addressing the public's concerns. Integrating both human and natural environmental concerns is an integral goal of their project development process and these concerns are willingly addressed.

Of interest to the delegation was also the level and impact of public involvement. The delegation concluded that all five countries involve the public in their project development process, although there were varied degrees and levels of involvement based on the project type and country. For example, the Scandinavians and Dutch have a more extensive and formalized process. Some concepts and methods used to involve the public in the project development were considered to be transferable to the U.S. and could prove beneficial in streamlining the existing practices. Moreover, the involvement of the public at the earliest stage possible was stressed by all governments to avoid potential conflicts and problems at later stages and when the project has reached a more concrete stage.

Some additional observations include the use of safety audits as an evaluation tool for the overall project development process, the development of project budgets at the end of the process, and the greater political role in the project development process. Finally, it was concluded that there is no single approach that can solve all potential problems in project development and a reasonable mix of practices is essential.

Environmental considerations
The main common concept among all countries is the inclusion of environmental issues as an integral part of the project, not as a separate issue. It was interesting to find that several countries have copied or adapted the U.S. Environmental Impact Study (EIS) process, but they have integrated this process more efficiently. Moreover, the Dutch believe that the environmental concerns are an everyday practice and are addressed sufficiently. Currently, they are considering means by which the regulations and process can be streamlined to reduce project completion time.

A general observation was that the highway agencies of these countries are more committed to addressing environmental issues and, in fact, most of the issues presented were human related including noise and historical preservation concerns. The reliance on non-governmental agencies to develop EIS was also presented as an alternative to identifying problems and possible solutions more easily and at the local level. For ease of project development and faster completion, projects are restricted to within the existing right-of-way, and when this is not feasible, mitigation is required. The concept of land redistribution was also presented as an alternative to mitigation which is a practice that could be promoted more in the U.S. Finally, European Union (EU) laws and directives regarding environmental issues play an important role and they should be addressed in the project development process.

Even though each country used a different term to describe their "design speed," all use a guiding speed for designing highways that ties the various roadway elements. Sweden, Denmark and the Netherlands have one suggested speed per road category (similar to functional class), while Germany and the United Kingdom have a range of speeds for each category, albeit more narrow than that suggested in the Green Book.

A roadway design philosophy common in all countries was the reliance on the physical roadway design to "enforce" operating speeds and the development of a "consistent" look for each road category. An interesting observation was the acceptance of lower operating speeds by the road users in these countries compared to the levels of acceptance in the U.S., a concept that may be reflected in their design approach of a self-enforcing roadway design.

Design flexibility
All countries utilize design guidelines for roadway design which are considered central to their design philosophy, and all have a design exception process where departures from design guidelines are addressed. This process is more frequently applied to non-motorways (equivalent to non-freeways). The public accepts more easily the lack of flexibility on motorways due to the purpose of these roads. Moreover, design flexibility is responsive to site-specific limitations and may be indicative of the wider acceptability of such design departures due to the fact that each problem area is addressed within its context and constraints.

It was also apparent that all these countries have dealt with or are currently dealing with a revision of their design guidelines and are at the point where their guidelines are geared to address road purpose and create a uniform look for each road category. This experience has allowed them to understand the value of design flexibility and exceptions. Finally, set documentation is required to justify departures from the design guidelines, which was very extensive in the United Kingdom possibly due to liability issues against the state.

Rural roads
High speeds on rural roads is also a safety issue for these countries and the focus is on attempts to control and reduce speeds. To achieve this objective, mobility is typically given up for the sake of safety. A common treatment to improve safety is the conversion of four-lane facilities to 2+1 facilities, where the middle lane serves as a passing lane in which the right-of-way alternates. Each country has customized this design to conform to their design guidelines and safety goals including varied roadway widths, lengths of passing lanes, and end treatment of passing lanes. All agencies indicated that there are capacity gains and safety improvements from this design and this design may be transferable to the U.S. Moreover, the four-lane conversions to 2+1 roads are typically performed within the existing right-of-way to reduce costs and implementation time.

Another approach for improving safety on these roads is the use of narrower lane widths, which require drivers to slow down. This approach is implemented either by physically providing narrower travelways or by visually decreasing the available width by creating wider edge lines or eliminating centerline striping. To further enforce the narrower roadway concept, clear zones are typically not provided and most roadway objects are shielded by guardrails. It should be pointed out here that these measures are applied to non-motorways where flexibility in design guidelines is present, contrary to motorways where the guidelines are more rigid.

Traffic calming
All countries are committed to reducing speeds through urban areas and are guided by the concept of integrating all modes and users in the same space. To achieve this objective, several practices have been implemented in urban areas including chicanes, islands, tables, cushions, humps, bumps, gates, landscaping, staggering, bollards, planting, pavement textures and colors, and optical narrowing (i.e., narrow travelway with markings). For a successful implementation, an area-wide strategy is required where a systemic rather than a localized solution is sought. This will enforce the concept of traffic calming for the entire area and will provide the driver with a clear and continuous message.

Moreover, proper design for the intended travel speed for each component is essential to provide discomfort to drivers exceeding the speed but not to those who travel at the desired speed. Community acceptance is also very important for a successful implementation. Most of these practices are transferable to the U.S. environment, but the differences in land use and development between Europe and USA must be recognized.

Roundabouts are used extensively in all countries (more than 1,000 each in four of the five countries) and are considered a very safe form of intersection. Safety studies in most countries indicate large reductions of fatality and injury crashes, although the reduction in the overall number of crashes is sometimes not as large. These empirical data on safety improvement can be used in the U.S. to support usage and implementation of roundabouts. These facilities can also improve intersection capacity over signalization, and those with single lane approaches seem to perform very well with volumes of up to 2,500 vehicles per hour due to their simplicity. These safety gains are typically due to reductions in speeds through the roundabout and, thus, mobility is reduced and delays to through traffic may be encountered.

To increase capacity, some countries are implementing multi-lane approaches and signalization, which may create safety issues. Roundabouts provide the designer with the flexibility to adjust the design to the site-specific conditions. An example of this flexibility is their use at interchanges by creating a teardrop design. The size of the roundabout is also an important and, at the same time, flexible design element and has an impact on the right-of-way requirements. An issue of concern is the interaction between vehicles and pedestrians and bicycles and how to integrate these users.

Bicyclists and pedestrians
Even though all countries consider and address the needs of bicyclists and pedestrians, there are two different philosophies regarding their level of consideration. Sweden, Denmark, and the Netherlands place a high importance in addressing the needs of these users and provide separate facilities as part of their network. Moreover, there is systematic effort to promote alternative use of transport modes and, thus, cycling and walking are heavily promoted with the Dutch government having the best plan.

On the other hand, Germany and the United Kingdom consider these users in their planning process, but they are given a lower importance than in the other countries. Another reason for this difference may also be the levels of demand which are lower in Germany and the United Kingdom than in the other countries. All five countries place an equivalent importance on the mobility needs of bicyclists and pedestrians in urban areas and are frequently given higher preference than mobility of vehicles.

An issue that all countries are struggling with is the integration of these users into roundabouts. Denmark and the Netherlands provide completely separate paths for these users, while the other countries provide paths within the same travelway. Finally, the under-reporting of bicyclists' and pedestrians' crashes is a concern in addressing safety levels and determining the most appropriate path type for these users.

In the European countries that were visited, the general philosophy for highway design and project development is primarily to develop a transportation program and system that enhances community values and integrates roadways into communities and the environment. This philosophy permeates their project development process, safety improvements, roadway design concepts, geometric design guidelines, and public involvement and environmental commitments. This is the essence of the recent push to promote the CSD approach in the U.S., and a shift toward this philosophy is supported by FHWA and several state DOTs.

Moreover, the roadway design philosophy of the Europeans is to develop a roadway that is designed for a specific purpose and addresses safety in a way that considers all users and implements an aesthetic approach to visually explain this concept. Finally, all countries have very high safety goals, ranging from zero fatalities to reductions of more than 40 percent in all crashes, which guide their design approach and philosophy. To achieve these goals they are willing to provide roadways that would self-enforce speed reductions, potentially increase levels of congestion, and promote alternative modes of transportation. This approach is somewhat contrasted with the U.S. situation where wider roads are deemed safer, there is a heavier reliance on signs to communicate the intended message, and there is a lower tolerance of congestion.

For more information, please contact John Okamoto at (206) 440-4691 or at