The goal of the workshop was to educate attendees on how to apply risk assessment and design flexibility to improve MnDOT’s return on investment while improving the compatibility of transportation projects with their settings, and the capacity of those projects to accommodate multiple modes.
The primary learning objective is the use of design flexibility to achieve solutions that are more context sensitive, with the intended benefits of higher rates of return on investments, better service to multiple modes, and higher effectiveness among practitioners in the application of flexibility in design. The workshop provides attendees with an overview of recent developments in current design issues, and basic knowledge of how to use flexibility to develop contextual designs.
Structurally, the workshop includes a total of 13 sessions over the course of 2.5 days, covering topics including safety (which is the main focus of day one), data, speed considerations, and geometrics. Each session entails a short presentation followed by a group exercise.
A summary of the content of each day is presented below, with specific feedback from the reviewers integrated throughout.
Jim Rosenow and Scott Bradley of MnDOT opened the workshop with an overview of MnDOT’s activities in the areas of CSS and Performance Based Practical Design (PBPD). They discussed the fact that Missouri DOT (MoDOT) was the first state to use the term practical design and the reasons why MoDOT attempted to change the way that projects are delivered. Mr. Bradley highlighted the several MnDOT case studies that have appeared in publications demonstrating successful application of CSS and PBPD.
Mr. Rosenow and Mr. Bradley then explained the need and power of flexibility in design. PBPD is a goal-oriented method of project delivery that is focused on using a broad set of criteria to solve a need, rather than jumping to a solution based on a single problem. However, PBPD does not mean that design standards are going away, rather designers need to work within them to make sure they are tuned correctly to make sense of the system and the need. The PBPD process is data-driven, as opposed to data-determined. In other words, data does not solely determine the decision—rather, practitioners of PBPD draw insights from the data in order to make informed decisions that also take into account the wider context of local conditions and economic realities.
MnDOT is increasingly understanding safety performance as a function of design, and recognizing the possibility for predicting crash rates based on geometric decisions in the design process. Until recently, the identification system provided in NCHRP 15-47: Developing an Improved Highway Geometric Design Process was used as a basis for design decisions, but opportunities now exist to refine that system based on better data. Improving system performance can greatly benefit the public. At this point, the presenters introduced the first exercise, which focused on building an understanding of return on investment (ROI).
Chris Roy, Deputy Director of Engineering Services at MnDOT, introduced the four elements of delivering projects successfully: safety, cost, meeting public expectations, and doing more projects, meaning that when projects are managed well and have met the other three elements, the department has the capacity to deliver more projects. He proposed that design exceptions present an opportunity to use good engineering judgement. Making good exceptions in the design process relies on data, experience, and diligent documentation.
Initial Feedback: None
The rest of the first day focused heavily on the issues of safety and the use of the traditional tools to address safety in design such as the HSM. Session 2 covered the changes in controlling criteria and sessions 3 and 4 covered risk reduction, safety improvement, and the use of the predictive model in the HSM.
Initial Feedback: PBPD could be better integrated into these sessions and likewise subsequent sessions. The principles and practices of defining context were not effectively applied to safety, and there was no discussion on the underlying causes of safety concerns or explanation of how context can impact safety.
Recommendations:
The final session of the day covered the importance of universal design, which is required under the Americans with Disabilities Act (ADA), and how to serve all transportation users. This session featured storytelling by Todd Grugel, MnDOT’s ADA representative, and Jaime Taylor of the Commission on the Deaf, Deafblind, and Hard of Hearing Minnesotans (MNCDHH). One statement from the presenters that appeared to resonate with the class was, “If it looks stupid, it probably is stupid”—meaning that if the design appears to be forced or wrong in relation to other elements around it, it likely will be unsuccessful. The instructors gave examples of a utility box directly in the path of a wheelchair ramp, and the bad placement of a crosswalk button with an audible signal. Compliance with ADA is the minimum—stopping at mere compliance is not always sensible. Flexibility and context are important for understanding real user needs and which measures will meet them effectively. This session effectively integrated the concept of maintaining flexibility while adhering to standards.
The day ended with two effective exercises. The first exercise involved walking outside and down the street with the presenters. Participants gained an understanding of the challenges faced by people with disabilities, and how standard street and sidewalk design can dampen effective ADA delivery. This exercise had a deep impact on the group and vividly demonstrated the importance of understanding the broader context of a transportation facility and its relationship to land use and users of varying ability.
The second exercise invited participants to try using a wheel chair to go up standard ramps, and to navigate a room with vision-impairing googles. The exercise illustrated that merely complying with ADA requirements does not always translate into a pleasant experience for users with disabilities.
Initial Feedback: None
These sessions covered the use of traffic data, but emphasized that designers should not focus solely on traffic. Focusing solely on peak period design may create problems during periods of non-peak traffic.
Initial Feedback: The content of these sessions was too basic for an advanced class. The presenter did not sufficiently explain how context impacts decisions or how flexibility should be applied when considering traffic, speed, and lane configurations. Traffic issues were explored reasonably well, but Level-of-Service (LOS) was the only metric explained.
The exercise on understanding multimodal level of service (MMLOS) did not cover the fundamentals of MMLOS and did not offer a thorough explanation of the issues it presents as a metric. The exercise was somewhat confusing and may have given the wrong impression regarding how MMLOS is calculated. The exercise also did not include setting targets for improvement, or looking beyond the existing constructed roadway to explore alternative solutions. MnDOT may wish to consider not starting with a premise in the exercise that a better MMLOS results in a degradation of single occupancy vehicle level of service—but rather consider the possibility that the facility may be over-built. (e.g. Road Diet considerations).
The design speed discussion was lively and acknowledged that context and function should inform the selection of design speed. However, during the exercise—when participants were asked to select a design speed for a corridor and explain their decisions—there was no discussion of the need to define the context or identify changes in land use. The absence of these elements begged the question—why modify any corridor elements and possibly lower the speed without understanding these factors?
Recommendations:
These sessions covered the topics of allocating space in conditions of a constrained right-of-way (ROW), the factors involved in horizontal alignment and superelevation, and the factors involved in vertical alignment and sight distances. The presenters provided an overview of lane widths, and why and when they apply. The primary focus was evaluating 12-foot and 11-foot lane widths in both rural and urban contexts. The presenters introduced NCHRP Report 783: Controlling Criteria for Geometric Design, specifically the recommendation for designers to consider 10-12-foot lanes for urban and suburban arterials.
Initial Feedback: The session covered the available guidance for considering lane width and allocating space, but did not explain the application of these tools or how they can assist with ensuring design flexibility. The segment about visual cues with regard to land use/activity, and how they can influence design, was effective. This session also included an overview of the fundamentals of intersection design. However, presenters did not provide an opportunity for participants to discuss the importance of context or the fact that, in some cases, volumes and speed may dictate design features that conflict with other features of the context. This section did introduce the concept of designing “from the outside in”—that is, considering the full context and then designing a street or roadway that fits into its built environment and accommodates all the users—but did not elaborate on why that approach is important.
The session about horizontal alignment devoted too much time to the issues of superelevation and side friction, while overlooking how context can influence alignment and geometric concerns. The exercise could benefit from imposing greater constraints to make it more challenging for participants and require them to think through how to accommodate the alignment through design flexibility. The workshop encountered similar issues with the vertical alignment discussion; the discussion centered too much on background without actually addressing flexibility or context.
Recommendations:
This session focused on freeway interchanges. The presenters provided an overview of various interchange designs, design components, and FHWA’s list of high-risk design elements. The presenters facilitated discussions regarding lane continuity, fork geometry, local connections, sight distance, geometric combinations, and vertical clearance.
The session ended with an exercise focused on interchange design. Participants were tasked with designing a freeway to support a hypothetical city land use plan, within a given context of community issues and land uses, and with preference given to developing a local road network connecting to the highway. Participants were instructed to design “from the outside in” but not given any information about what that means.
Initial Feedback: The discussions about lane continuity, fork geometry, and other key concepts were fairly basic and straightforward. They also did not sufficiently cover how flexibility can be achieved to fit context and performance. Additionally, the participants should have been given clearer instruction about what it means to design “from the outside in.”
Recommendations:
This session covered roadside design. The presenters discussed clear roadside concepts, provided an overview of American Association of State Highway and Transportation Officials (AASHTO) guidance, and explained the criteria in MnDOT’s Road Design Manual. The discussion on clear zone emphasized the concept of flexible design and the fact that the widths noted are only guidelines and not standards. The concept of additional considerations when determining the clear zone width was also presented.
Initial Feedback: None
This session covered retrofit designs. Compared to the earlier sessions, the presenter of this session spent more time explaining CSS and particularly PBPD in greater detail, specifically in terms of interchange treatments, ramp designs, operational alternatives. Participants were asked to consider how modifications can be made using materials already available, without needing to fund expensive improvements.
Initial Feedback: The discussion about completing modifications affordably would have benefited from greater attention to context and alternative measures that include greater design flexibility. Also, it was unclear why this discussion on modifications was included in the session about retrofits.
The workshop was concluded with a roundtable discussion of key takeaways: what participants had learned, what implementation challenges they anticipate, and what additional information and guidance they need. Noteworthy comments included:
