The National Academies Press

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From page 49... ... 49 There are certain guiding principles that should shape and define an effective process into the future. The research team characterizes these guiding principles in three categories -- the fundamental bases for road design, the social and public policy framework within which the process is conducted, and the necessary attributes of an effective process. Read the entire page →
From page 50... ... 50 a performance-Based highway Geometric Design process minimum dimension, but does not reward or incentivize the designer from using more than the minimum dimension. The application of a green line model (nominal safety) Read the entire page →
From page 51... ... Guiding principles for an effective 21st Century highway Design process 51 optimal performance for an acceptable implementation cost, such combination and cost reflecting the specifics of the context. The second of the threefold implications of the guiding principle is that the geometric design process must be viewed as incorporating continuous change. Read the entire page →
From page 52... ... 52 a performance-Based highway Geometric Design process controlled access facilities. Another example may be the design of a parkway for which trucks are prohibited. Read the entire page →
From page 53... ... Figure 16. Value proposition: reliable travel time. Read the entire page →
From page 54... ... 54 a performance-Based highway Geometric Design process or should be quantifiable in any geometric design context. The point of this comparison and qualitative analysis is to demonstrate that incorporation of operational solutions or features can and should be part of the geometric design process and decision-making process, rather than a separate or after-the-fact process. Read the entire page →
From page 55... ... Guiding principles for an effective 21st Century highway Design process 55 unforeseen changes in the context will occur, and roads designed using models will not always perform as expected or intended. Such uncertainty cannot be overcome with additional data, greater investment in technology, or more detail in the engineering. Read the entire page →
From page 56... ... 56 a performance-Based highway Geometric Design process by urban and rural; three levels of functional classification; and three levels of terrain is insufficient to fully capture all relevant context factors. The geometric design process needs a more robust set of context definers, and the design process should support or direct design decisions, dimensions, and choices consistent with the defined context. Read the entire page →
From page 57... ... Guiding principles for an effective 21st Century highway Design process 57 began to influence project development. The progression of questioning and input by these stakeholders lead to the passing of the NEPA and other subsequent legislation. Read the entire page →
From page 58... ... 58 a performance-Based highway Geometric Design process and lasting functional value) , resource allocation (funds allocated for construction and maintenance) Read the entire page →
From page 59... ... Guiding principles for an effective 21st Century highway Design process 59 other reports. Best practices change over time as the knowledge base and technology improvements come into being. Read the entire page →
From page 60... ... 60 a performance-Based highway Geometric Design process certain design exceptions (Mason and Mahoney 2003) , and the lack of widespread adverse safety performance consequences when these are appropriately applied (Stamatiadis et al. Read the entire page →
From page 61... ... Guiding principles for an effective 21st Century highway Design process 61 4.2.2.2 Driver Licensing and Traffic Law Enforcement Other aspects of the legal framework include laws and regulations associated with licensing of drivers, passage and enforcement of traffic laws, and definitions and restrictions on legally operable vehicles. The engineering profession must assume that driving will continue to be a highly regulated privilege in which drivers are repeatedly tested and licenses are issued, suspended, and revoked based on driver behavior and physical capabilities. Read the entire page →
From page 62... ... 62 a performance-Based highway Geometric Design process play a direct role in the geometric design process that is no less important than that of the highway design engineers. Again, what often results is a design exception to address a regulatory constraint or issue. Read the entire page →
From page 63... ... Guiding principles for an effective 21st Century highway Design process 63 produces the intended driver/vehicle/roadway system performance. This also may be an outcome produced by self-driving vehicles. Read the entire page →
From page 64... ... 64 a performance-Based highway Geometric Design process As a final example, consider the concept of the design domain, which is evident in design practices in many Canadian provinces. This principle acknowledges the practicalities of selecting design dimensions for a reconstruction road project to be in concert with the prevailing dimensions of the road and network to which the reconstructed road will be attached. Read the entire page →
From page 65... ... Guiding principles for an effective 21st Century highway Design process 65 the practical limitations of both the project's context and the available resources set by the agency's policymakers and sponsors. Transportation agencies do not just design and construct roads. Read the entire page →
From page 66... ... 66 a performance-Based highway Geometric Design process • The process must be executable by properly trained professionals in a consistent manner, • The process should be transparent, and • The process must be defensible. 4.3.1 Efficiency Efficiency refers primarily to the data required and tools or methods that are core to process execution. Read the entire page →
From page 67... ... Guiding principles for an effective 21st Century highway Design process 67 minimized. This is done through the appropriate, timely application of the full range of tools listed in Table 3, using readily available agency and project-specific databases. Read the entire page →

From page 49...

... 49 There are certain guiding principles that should shape and define an effective process into the future. The research team characterizes these guiding principles in three categories -- the fundamental bases for road design, the social and public policy framework within which the process is conducted, and the necessary attributes of an effective process.