In CSS projects, close scrutiny is given to the design of pedestrian and traffic barriers, sound and visual barriers, and the dimensions and design elements within a "clear zone."
Excerpt
Cross-Section Elements: Traffic barriers "The purpose of the barrier... [is] to minimize the severity of potential accidents involving vehicles leaving the traveled way where the consequences of errant vehicles striking a barrier are less than leaving the roadway....A wide variety of traffic barriers is available for installation along highways and streets, including both longitudinal barriers and crash cushions. Longitudinal barriers (such as guardrails and median barriers) are designed primarily to redirect errant vehicles and keep them from going beyond the edge of the roadway....The design of the traffic barrier is an important detail that contributes to the overall look or theme of roadway design." more...
from
Flexibility in Highway Design
Excerpt
Cross-Section Elements: Clear Zones A clear zone is "the unobstructed, ... flat area provided beyond the edge of the traveled way for the recovery of errant vehicles ... The width
of the clear zone is influenced by ... traffic volume, design speed of the highway,and slope of the embankments."
more...
Use sturdy fixed security bollards to replace concrete barriers. Protect critical
infrastructure and allow pedestrians to move freely.
Create new secure areas, and pedestrian zones with retractable bollards.
-- Transportation Alternatives
Article / Paper / Report
California Highway Barrier Aesthetics
This report will familiarize designers with current barrier design options, and encourage
appropriate aesthetic considerations to develop visually pleasing context sensitive solutions for
highway projects. Technical guidelines allow integral color, paint, stain, and subtle textures to be incorporated with
concrete barriers placed on highway transportation projects. These guidelines address highway
corridor aesthetic issues, and respond to concerns from local communities and agencies for more
barrier design alternatives that are context sensitive without compromising safety considerations.
-- California Department of Transportation
Article / Paper / Report
Crash Testing of Various Textured Barriers
New methods of forming concrete walls and barriers have provided designers with a wide
variety of possible architectural treatments in the form of patterns and textures. However, there
are limited crash test data to verify that barriers featuring these patterns and textures will comply
with National Cooperative Highway Research Program (NCHRP) Report 350 crash testing
criteria. There is a need to develop guidelines for evaluating the crashworthiness of barriers with
a broad range of patterns and textures based on full-scale crash testing of selected representative
designs.
-- California Department of Transportation
Website
Aesthetic Barrier Systems (opens in a new window)
This website by the Eastern Federal Lands Highway Division of the FHWA illustrates aesthetic barrier systems like steel-backed timber guardrails, steel masonry guardrails, and precast concrete guardrails.
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Federal Highway Administration
Article / Paper / Report
Concrete Barrier Texture Guidelines
This letter from the California Department of Transportation discusses general texture guidelines for use on single-slope concrete barriers.
Traffic Barriers, Barrier Terminals, Crash Cushions, and Bridge Railings
Breakaway Hardware
Work-Zone Devices
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Federal Highway Administration
Article / Paper / Report
Enhancing Rural Roadside Safety
A forgiving environment anticipates drivers' mistakes,
allows time and space for making driving corrections,
and minimizes potential hazards for errant vehicles.
Potential hazards include bridges, poles, trees, guard
rails, mailboxes and, most frequently, ditches or
embankments.
In short, just about anything in the right of way that
can be struck by an errant vehicle is considered a
potential hazard.
A clear zone is a transversable area that is adjacent to
the driving surface and has no fixed objects. Clear zone
widths vary from over 30 feet to 10 feet or less, based
on several factors like traffic volumes and speeds,
roadway geometrics and classification, and foreslope
characteristics.
-- Center for Transportation Research and Education (CTRE) - Iowa State University
Article / Paper / Report
Risk-Management Handbook: General Liability - Improving Roadside Safety
Road design cases continue to be a leading liability loss driver for NYMIR subscribers. Road design cases usually stem from an auto accident where injuries are sustained, and a claim is made against the municipality that owns or controls the road. In many cases, the claimants are individuals who were injured in single-car accidents where the vehicles ran off the road, and hit a stationary object or overturned. The lawsuits typically allege improper design; inadequate signage; failure to correct roadway and roadside hazards and dangers; improper traffic control devices, and unsafe construction zones. Road design cases differ from road maintenance cases. With the latter, claims usually allege failure to provide a reasonably safe roadway - usually improper removal of snow or ice, not cutting back vegetation, failure to remove excess gravel or sand, and improper pothole repairs. The National Safety Council1 indicates there were 12,300 fatal and 290,000 injury accidents as a result of a collision by a motor vehicle with a fixed object - usually a tree, utility pole, guardrail, or abutment. According to the Cornell Local Roads Program, run-off-road collisions accounted for 13 percent of all crashes in New York in 2000 and 27 percent of fatal crashes.
-- New York Municipal Insurance Reciprocal (NYMIR)
Article / Paper / Report
Safer Roadsides
By 2007, FHWA would like to reduce fatalities involving roadway departure crashes by 10 percent--one of the goals of the agency's Vital Few strategy. (Road departure crashes include both ROR and head-on crashes and are combined into one category because similar countermeasures can be used to tackle both problems.) To meet this objective, FHWA's approach includes research, working cooperatively with other organizations, and developing and implementing strategies such as a new computer analysis tool.
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Federal Highway Administration
Excerpt
The Roadside: Flexibility in the AASHTO Guidelines The AASHTO Green Book (2) is intended to be flexible with respect to roadside design treatments.
It refers to the Roadside Design Guide (3) for use in general guidance; as noted previously, there may well be more than one solution that is acceptable for a given location. The Roadside Design Guide (3) also states this in its preface. more...
from
A Guide for Achieving Flexibility in Highway Design
Excerpt
Roadside Clear Zone: Flexibility in the AASHTO Guidelines Designers need to understand the nature and proper use of the Roadside Design Guide (3). While clear zone dimensions are provided in this guide, they should not be viewed as either absolute or precise. It is expected that the establishment of roadside design criteria and the design of the roadside is a site- or project-specific task for the designer. more...
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Historic Columbia River Parkway Columbia River Gorge, OR
The first paved highway in the northwestern United States, the Columbia River Highway was conceived, designed, and constructed as both a scenic attraction and as a means of facilitating economic development along the Columbia River corridor between the Pacific Ocean and the areas to the east of the Cascade Mountains. The history of the development, decline, and continuing rebirth of the Columbia River Highway is particularly instructive to the highway engineering community as we approach the beginning of a new century and a future of increasing reliance on the rehabilitation and restoration of existing infrastructure instead of the construction of new highways. This study also illustrates the manner in which state and local governments can preserve and enhance existing highways that possess unique scenic and historic qualities within the framework of modern design criteria.
Aesthetic Guardrail Design, SR-20 - Ducken Road to Rosario WA
The purpose of this project is to improve safety and reduce accident frequency and severity. Within this section of SR-20, a primary issue is upgrading it to bike touring standards.
Added Capacity and Noise Walls - SR-527 Mill Creek, WA
This project was developed to address congestion on a section of SR-527 between 164th Street SE and 132nd Street SE. SR 527 highway passes through downtown Mill Creek.
"The term 'clear zone' is used to designate the unobstructed, relatively flat area provided beyond the edge of the traveled way for the recovery of errant vehicles. The clear zone includes any shoulders or auxiliary lanes."
The type of traffic barriers you choose is an important consideration along scenic byways. Barriers help prevent motorists form striking a more hazardous object or from sliding down a steep slope. However, since these structures line the roadway, they also influence the scenic quality.
Several aesthetic alternative barriers have been designed and tested to complement the natural landscape or reflect an architectural theme better than traditional barriers. Naturally weathering steel guardrails may be an improvement over the highly reflective galvanized rails. Other choices include wood rails with steel backing, stone walls with a concrete core, precast simulated stone guardrails, and glue-laminated wood guardrails. All have been crash tested and approved by the FHWA.
Barrier standards and designs along high-volume roads or freeways do not always apply to low-to-moderate-volume roads. Roadside berms can be another alternative. Work with transportation engineers to select the best alternative for the type of road and location.
Fences and walls can make a positive contribution to the character of byways. Sometimes, they are one of the defining features of an area, such as the white horse fences of Kentucky or the stone walls of Kansas. There are almost as many types of fences and walls as there are applications for them. The design of those barriers should not only consider the function, but also the aesthetic qualities of the landscape in which they are located.
The design should reflect the landscape context and/or the design theme of the byway. Compatibility can be enhanced by using materials characteristic of the area or of nearby structures or developments.
Human scale is critical, especially where people will be in close proximity. Large, obtrusive barriers can dominate views. The relationship between the height, the width of panels, and the post sizing are important considerations.
Poorly designed and constructed fences and walls can detract and even dominate the scenery along a byway. On the other hand, if sensitively planned, designed, and constructed, ther may complement their surroundings by dramatizing selected views and adding interest to the landscape.
