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Design Criteria for Modal Conflicts


Consideration of all users is a central consideration continuing to emerge during the design phase of roadway projects. The commonly implemented concepts of Context Sensitive Solutions and Complete Streets, for example, encourage inclusion of design considerations for additional roadway functions. It is well recognized that streets serve many purposes to many users; however, the specific design criteria for multiple users are many times conflicting (e.g., pedestrian-focused accommodations favor shorter crosswalks (roadway width) and tighter curb radii; truck-focused accommodations support the opposite-- wider roadways and largercurb radii). In regards to recognizing that the role of the design engineer is to balance the various needs of multiple users of the roadway, limited national engineering science-based guidance exists to assist. Furthermore, such research has been conducted in understanding best practices for many street functions individually; however, few tools exist to weigh the sometimes conflicting needs of various users. The reliance on the personal experience and opinions of the designer, rather than an accepted, peer-reviewed and published scientific-based method, results in drastic non-uniformity of roadway design and prioritization as well as success. It is envisioned that the results of this research statement will outline a science-based framework for a design tool/method which can be applied by practitioners during the design process.


The objective of this research is to produce a science-based analytical method to quantify and compare the road design needs of multi-modal users as they relate to one another within the same spatial constraints. An interim product of this research will be a technical method to measure the impact of infrastructure design on meeting the needs and attractiveness of different modes.

The final product of this research should create a tool that will help transportation design professionals to better understand the general roadway tensions between multiple transportation modes and their associated design elements and requirements. The project should result in design guidance that recognizes the reality of how multi-modal environments geometrically influence one another.


Creating safe and efficient multi-modal transportation environments is a high priority in urban areas and will only be more expansive in the future. Many urban roadway projects are advanced annually that could incorporate the findings of this research. As stated earlier, there is very limited engineering science on this topic to assist practitioners, municipalities and state DOTs. The lack of national research on this subject is requiring agencies to conduct their own individual analysis at their expense and using design waivers when necessary.

Related Research:

A search was conducted and resulted in no related multi-modal roadway design research within TRIS or RIP results containing the following search terms: “Multi-modal roadway design” and “Multi mode design”.

Prior research has reviewed the history of aesthetics in American roadway design (1) as well as the unique contemporary environmental and social needs surrounding the road facility, commonly manifested under a Context Sensitive Solutions framework (1, 2). Many of these documents outline the engagement process (3) to define successful goals and measures for a project but do not include specific design guidance to achieve a project’s success.

The increased recognition of alternative transportation modes and non-transportation road uses has led to the research and development of new guidelines and measurements. For example, much research has been done to identify impacts to Multi-Modal Level of Service; however, the level of service measures are focused on measuring operational throughput rather than the contextual quality of the physical design of a facility (8). Furthermore, current research examines these multiple modes and their associated physical design requirements and impacts (4-7) but fails to fully address how one roadway user’s need will affect (often adversely) the other.

Sponsoring Committee:AKD10, Performance Effects on Geometric Design
Research Period:24 - 36 months
RNS Developer:Andy Kaplan, Philip Demosthenes, Aimee Jefferson
Source Info:Problem statement developed as a result of the Safety Effects of Geometric Design Decisions Workshop at the 2013 mid-year meeting of TRB Committees AFB10 (Geometric Design), AHB65 (Operational Effects of Geometrics),and AHB70 (Access Management).
Date Posted:07/07/2014
Date Modified:07/15/2014
Index Terms:Context sensitive design, Context Sensitive Solutions, Complete streets, Geometric design, Highway design, Multimodal transportation, Best practices,
Cosponsoring Committees: 
Pedestrians and Bicyclists
Operations and Traffic Management
Safety and Human Factors

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