This section provides an overview of CSS. What it is and how it can help to shape transportation projects around the country. Feel free to browse through the topics below or search for a particular page by entering a keyword in the search box below or clicking on "Advanced Search."
In CSS projects, designers are using the flexibility inherent in design criteria and standards to select a lane width that is appropriate to a site's context, the desired vehicular speed, and types of vehicles served, recognizing that roadway space is often constrained and excess space for vehicles can be given over to other purposes, such as wider sidewalks for pedestrians or a bicycle lane.
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Considering Scale People driving in a car see the world at a much different scale than people walking on the street. This large discrepancy in the design scale for a car versus the design scale for people has changed the overall planning of our communities. more...
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Flexibility in Highway Design
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Road Width The design element with the greatest effect on the scale of the roadway is its width, or cross section. Elements (or a lack of elements) along the roadside also contribute to the perceived width of the road and can even affect the speed at which motorists travel. more...
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Flexibility in Highway Design
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Cross-Section Elements: Travel Lanes "The number of lanes needed for a facility is usually determined during the concept
stage of project development. It is usually the number of lanes necessary to accommodate the expected traffic volumes at a level of service determined to be appropriate for the facility." more...
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Flexibility in Highway Design
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Cross-Section Elements: Lane Width "The width of travel lanes is limited by the physical dimensions of automobiles and
trucks to a range between 2.7 and 3.6 m (9 and 12 ft)." Surrounding context and speed are factors determining the necessary minimum lane width. more...
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Flexibility in Highway Design
Article / Paper / Report
Road Diets: Fixing the Big Roads
Nationwide, engineers are putting roads on "diets," helping them lose lanes and width. In the process formerly "fat" streets often become leaner, safer, and more efficient. They become multi-modal and more productive. In many cases these former "warrior" roadways are tamed and turned into "angels."
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Dan Burden
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Lane Width: Flexibility in the AASHTO Guidelines The AASHTO Green Book (2) recognizes the need for flexibility and provides that flexibility, citing how lane width can be tailored, to a degree, to fit the particular environment in which the roadway functions (e.g., low-volume rural roads or residential areas versus higher volume rural or urban facilities). The formulation of these values demonstrates considerable flexibility. more...
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A Guide for Achieving Flexibility in Highway Design
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Lane Width: Mitigating Narrow Lanes The operational and safety effects of lane width are combined with those of other cross sectional elements. Knowledge of the total effects of lane width, shoulder width, and the roadside offers insights into mitigation when less than desirable lane widths may be necessary. more...
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A Guide for Achieving Flexibility in Highway Design
from
A Guide for Achieving Flexibility in Highway Design
Case Study
San Bernardino San Bernardino, CA
"...a vision for the rebirth of downtown San Bernardino, one that builds upon the steady progress of a revitalization effort already in the works and that directly responded to the needs the community revealed."
Case Study
Highway through Aabenraa, Denmark Aabenraa,
"The three-km-long, heavily trafficked highway through Aabenraa has been converted according to the principles of environmentally adapted through roads, with due respect paid, however, to the substantial traffic flow. This has reduced car speeds, has made a coherent bicycle route network, has resulted in a falling number of accidents, and has increased the feeling of security for the light road users."
Case Study
Shopping Street in Vordingborg, Denmark Vordingborg,
"The main shopping street in Vordingborg, Algade, has been converted from a one-way street to partly a pedestrian street, partly a 30 km/h street with commercial traffic allowed in both directions. The conversion has embellished the street and reduced car traffic volume and speeds considerably."
Case Study
Town Street in Naestved, Denmark Naevstved,
"As part of an extensive reconstruction of the street network in the town center of Naestved, Ramsherred has been converted to a pedestrian street with one-way business-related motor car traffic allowed. What used to be an ordinary town street with much too narrow sidewalks is now in its entire width designed on the premises of the light road users."
"We established goals and developed design concepts with the task force from building face to building face rather than from curb to curb. we considered lane widths in light of the whole road as it passes through the town. If we went from 10-foot lanes to 11-foot, would the impact on pedestrians, on trees, on the entire context be worth that extra foot? Everyone developed and understanding of the implications, and we were able to reason together."
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Dan Uebersax, Landscape Architect, Maryland State Highway Administration
