White Papers for Right-Sizing Transportation Investments (2020) / Chapter Skim
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Pages 69-103
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From page 69... ...
69 White Papers for Right-Sizing Transportation Investments 4. Right-Sizing Project Design 4.1.
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From page 70... ...
70 White Papers for Right-Sizing Transportation Investments project is designed in a manner consistent with the context of the roadway, advocating strong consideration of community, neighborhood, and environmental values. (More information on this concept can be found at http://www.ite.org/css/)
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From page 71... ...
71 White Papers for Right-Sizing Transportation Investments commonly used in case law, guidance, and general practice.) The project Purpose and Need statement drives the process for alternative consideration, in-depth analysis and ultimate selection.
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From page 72... ...
72 White Papers for Right-Sizing Transportation Investments The DOT has found that reallocation of the space in the right locations can increase the safety and operation of the corridor, and, provide local agencies an opportunity to grow their network of bike and pedestrian infrastructure and align with existing complete streets. Within the DOT's business process, a number of factors are usually considered to determine the feasibility of converting a four-lane roadway to a three-lane roadway, those being: Roadway function and environment Overall traffic volume Level of operational service Turning volumes and patterns Frequent-stop and/or slow-moving vehicles Weaving, speed and queues Crash types and patterns Pedestrian and bike activity Right-of-way availability, cost and acquisition impacts General characteristics: parallel roadways, offset minor street intersections, parallel parking, corner radii, and at-grade railroad crossings.1 These factors are usually analyzed at a corridor level and require significant data gathering and analysis to determine feasibility.
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From page 73... ...
73 White Papers for Right-Sizing Transportation Investments 12,000)
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From page 74... ...
74 White Papers for Right-Sizing Transportation Investments flexibility, a designer should select features that are compatible with the project "purpose and need," and developed under a performance-based practical design process, meaning that an analysis should be made of the impacts of primary design elements using measures of safety, operations, access and other criteria established by the agency and stakeholders. It is also worth noting from these design approaches that certain aspects of a right-sizing mindset can be set up so as to become "standard operating procedure." Interviews conducted with KDOT in support of this white paper, in addition to interviews with five other states conducting during the preparation of NCHRP Synthesis 443, Practical Highway Design Solutions, found this to be the case.
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From page 75... ...
75 White Papers for Right-Sizing Transportation Investments greenfields are urbanizing, it is essential to apply best practices, and thereby solve tomorrow's problems, before they become problems. In many rapidly-growing areas, there is often pressure to pursue "greenfield" development.
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From page 76... ...
76 White Papers for Right-Sizing Transportation Investments Figure 15 "Ideal Network" vs. Actual Salt Lake County Network Source: Metro Analytics Not surprisingly, throughways in the sparse areas are overwhelmed with congestion, serving longdistance freight and commutes, while also serving local trips, such as shuttling kids to soccer games.
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From page 77... ...
77 White Papers for Right-Sizing Transportation Investments Figure 16 Comparison of development road network configurations Source: StreetPlan.net At the other end of the spectrum are suburban "super-grids" and more haphazard networks. Super-grids are common where farm access roads along USGS section-lines became the default "plan" for urban arterials, and everything in between was left to individual developers, who historically derived their maximum value with cul-de-sacs and discontinuous streets.
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From page 78... ...
78 White Papers for Right-Sizing Transportation Investments Figure 17 displays a selection of streets in Salt Lake County. Near downtown, South Temple divides the "Avenues" district, which has three-acre blocks, from the rest of downtown which has famously large 10-acre blocks.
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79 White Papers for Right-Sizing Transportation Investments accumulated on windy, dendritic interior streets. The difference is that dendritic streets offer very little utility to alternative modes or to drive trips much beyond half a mile.
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80 White Papers for Right-Sizing Transportation Investments arterial and create flexibility for the future. Developers could have flexibility in the curvilinear nature of these back-side streets.
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81 White Papers for Right-Sizing Transportation Investments Summary of Right‐Sizing for Greenfields Adopt a minimum standard for continuous streets, ideally ¼ mile to ½ mile. Avoid rigid right-of-way standards such as "84 feet for minor arterials, and 110 feet for principal arterials." Instead evaluate each street within its network context, desired use typology, and include Complete Street elements from the beginning, or have a plan for including them later.
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From page 82... ...
82 White Papers for Right-Sizing Transportation Investments Table 12 Rule-of-Thumb Traffic Volumes at Which Facilities Tend to Show Signs of Distress Source: Metro Analytics, derived from Florida‐based research and microsimulation assuming 10% of AWDT occurs in PM peak hour. As another example, suppose a four-lane arterial (no center-turn lane) currently carries 22,000 ‒ well below its 28,000 ability ‒ but a "road diet" to change it to three lanes could result in significant congestion, as three-lane highways are challenged much above 20,000.
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From page 83... ...
83 White Papers for Right-Sizing Transportation Investments the community is encouraging a mix of uses at higher intensities than before, then it is easily predictable that a 45 mph highway will result in serious accidents if such uses materialize. However, it is also possible that a decision not to change the typology to a 30-35 mph design will impede the market for the community's land-use desires, and hence there will continue to be no apparent pedestrian safety problem because there remain few pedestrians.
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From page 84... ...
84 White Papers for Right-Sizing Transportation Investments Another interesting angle to trip length analysis is that 30,000 could be 30,000 ‒ or it could be 60,000. In the top example, if all 30,000 trips go from one anchor to the other, then there are truly 30,000 unique trips.
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From page 85... ...
85 White Papers for Right-Sizing Transportation Investments Figure 23 Illustrative comparison of development and taxes generated Source: Urban3 and Strong Towns In Figure 24, green areas are revenue positive, while red are revenue negative in a lifecycle analysis. Notice that in this case it's the lower-income neighborhoods that are generating more revenue relative to their infrastructure burden, most likely because it is higher density.
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From page 86... ...
86 White Papers for Right-Sizing Transportation Investments 4.6. What Does Right-Sizing Look Like?
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87 White Papers for Right-Sizing Transportation Investments Many stakeholders are also pushing for speeds as low as 30 mph. However, the senior engineer in the room pushes back, noting this is still a congested corridor despite having lost much business, and downsizing to just one left-pocket, as well as a speed reduction from 45 to 30 mph, is simply unacceptable.
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From page 88... ...
88 White Papers for Right-Sizing Transportation Investments Figure 26 Illustrative design concept enabled by alternative intersections Source: StreetPlan.net Illustrative Right‐Sizing Via Multi‐Way Boulevards (Upsizing) The previous example discussed right-sizing as downsizing.
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From page 89... ...
89 White Papers for Right-Sizing Transportation Investments Figure 27 Illustrative design concept: from typical arterial to multi-way boulevard Source: StreetPlan.net 4.7. Considerations for Right-Sizing Freeways Figure 28 is a satirical rendering of where we could end up if we continue to try to build our way out of freeway congestion.
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From page 90... ...
90 White Papers for Right-Sizing Transportation Investments freeways more likely upsize than downsize, it explores reasons to avoid upsizing, and offers strategies for matching demand to limited supply. When Freeway Right‐Sizing Means Downsizing The list of cities that have removed freeways is growing: Portland, Milwaukee, San Francisco, Rochester, and internationally in Seoul, Korea, and Madrid, Spain.
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From page 91... ...
91 White Papers for Right-Sizing Transportation Investments requirements, and possibly even lower height clearance requirements. If there is significant through traffic, the choice need not be just between Big Dig tunneling to support 60 mph traffic underground or stop-n-go averaging 10 mph traversing stop-lights on boulevards.
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From page 92... ...
92 White Papers for Right-Sizing Transportation Investments Figure 30 Example, I-345 in Dallas Source: Patrick J. Kennedy, Space Between Design Studio. Finding an End to Endless Upsizing Equally challenging in the right-sizing debate is when freeways have little room left for additional lanes. They crawl along in stop-n-go conditions and projections show future traffic would easily fill any new capacity (if it were possible to create)
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From page 93... ...
93 White Papers for Right-Sizing Transportation Investments Managed Motorways: This is a technique that is proving politically possible today. It was pioneered in Australia and is likely to be implemented soon in the United States.
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From page 94... ...
94 White Papers for Right-Sizing Transportation Investments Existing trends with the popularity of ride-share apps like Uber and Lyft, along with rising generations more inclined to use rental services of all kinds, and technologies such as managed motorways all portend that deciding now to continue super-sizing freeways could soon prove to be a great waste of resources that otherwise could have been used for improving other aspects of the transportation system. Curve of Diminishing Returns: At a certain point, the cost per lane mile goes up exponentially, while incremental capacity gained is barely noticeable given inefficient lane utilization, weaving effects, and higher propensities for system-crippling incidents.
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95 White Papers for Right-Sizing Transportation Investments Figure 31 Wide single-family residential street Source: Metro Analytics Two-Way Yield Street: In Greenfield development, this can be improved easily with a "yield street" configuration as shown in Figure 32 and recommended in NACTO's "Urban Streets Design Guide." When two cars are parked across from each other, only one vehicle will fit through. But since parking will usually be less than fully utilized, it is easy for one vehicle to pull-over while the other moves through.
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From page 96... ...
96 White Papers for Right-Sizing Transportation Investments Figure 33 One-way residential street Source: StreetPlan.net Right-Designing with Tree Zippers: There are many depressed value, single-family neighborhoods where infill is desired. If these neighborhoods can be reinvigorated, it will deter the need for new infrastructure on the fringes.
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From page 97... ...
97 White Papers for Right-Sizing Transportation Investments Right‐Sizing School Zones and Pedestrian Zones When a street is first built, the adjacent uses that emerge next can render the street "wrong" for the situation. For example, three-lane collectors with under-utilized shoulders are very common street types, and unfortunately it is also very common for public schools to be built adjacent to such streets.
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From page 98... ...
98 White Papers for Right-Sizing Transportation Investments Right‐Sizing with Place‐Making Alternative Intersection Design High-efficiency intersection design strategies are just starting to catch on nationally. Continuous flow intersections (CFI)
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From page 99... ...
99 White Papers for Right-Sizing Transportation Investments The Place-Makers: Quadrant intersections, thruturns, and town center one-way couplets are the high-efficiency designs with the most placemaking potential.55 This paper will briefly consider just the quadrant design. First imagine a typical, huge suburban intersection with double-left pockets on all approaches.
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From page 100... ...
100 White Papers for Right-Sizing Transportation Investments the situation find they cannot do much because they feel they must manage traffic and are unable to do so without "double-lefts" and other features that detract from livable environments. Figure 38 is a depiction comparing the stroad intersection to the redesigned intersection that relies on the quadrant design.
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From page 101... ...
101 White Papers for Right-Sizing Transportation Investments turns. The presence of backage roads does not require left rerouting, but they do make it possible to do so at any time.
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From page 102... ...
102 White Papers for Right-Sizing Transportation Investments are other "d-strategies" to evaluate that can help reduce demand to make room for other things. And even when direct new capacity is a good idea, there are place-making methods for increasing vehicle capacity, as noted earlier, and these should be included for analysis to discern their applicability over more auto-oriented capacity solutions.
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From page 103... ...
103 White Papers for Right-Sizing Transportation Investments region-wide political support. However, if you packaged dozens of arterials together into a single marketable "billion-dollar project," this might create a situation in which everyone stands to gain something, and therefore funding can be secured.
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