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Highway Traffic and Safety Analyses Lecture 21: Identifying Safety Deficiencies and Countermeasures Purdue University School of Civil Engineering West Lafayette Reading Assignment GUIDELINES FOR ROADWAY SAFETY IMPROVEMENTS, October 2006, link .
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Lecture 21: Identifying Safety Deficiencies and Countermeasures
School of Civil Engineering
GUIDELINES FOR ROADWAY SAFETY IMPROVEMENTS, October 2006, link.
Chapter 5: SAFETY REVIEW OF HIGH CRASH LOCATIONS, Pages 27-46
Formal examination of an existing or future road or traffic project by an independent team of trained specialists to identify road safety deficiencies.
Stages of safety audits = Stages of a road project
Feasibility Study -- scope of a project, route choice, selection of design standard, impact on the existing road network, route continuity, provision of interchanges or intersections, access control, number of lanes, route terminals, stage development, and more.
Preliminary Design -- horizontal and vertical alignment, sightlines, intersection layouts, land and shoulder width, pavement side slope and superelevation, overtaking lanes, provision for parked and stationary vehicles, provision for cyclists and pedestrians, effects of departures from standards and guidelines, safety during construction.
Detailed Design -- line markings, signing, delineation, lighting, intersection details, clearances to roadside objects, provision for road user groups with special requirements (for instance, pedestrians, cyclists, people with disabilities, trucks and buses), temporary traffic management and control during construction, drainage, poles and other roadside objects, landscaping, slopes and guard fencing.
Pre-opening -- the audit team would walk or drive through a project to check on the quality of completed safety features. They would inspect many of the same items as were considered during the design process, and they would try to be at the project during different conditions--day and night, wet and dry, etc.
In-service -- identifies weaknesses in the functioning of safety features while the road is open to motorists.
STAGE 2: DRAFT DESIGN
2.2 DESIGN ISSUES (GENERAL)
1 Geometry of Horizontal and Vertical Alignment
1A Does the horizontal and vertical design combination of the road provide a suitable alignment for drivers?
1B Do the combinations of horizontal and vertical design elements conform to design practice? (i.e. there shouldn’t be undesirable combinations of horizontal and vertical design)
1C Is the design free of cues that would cause a driver to misread the road characteristics? (e.g. visual illusions, confusing delineation of lines of trees, poles, etc.)
1D Does the alignment selected ensure speed consistency?
1E Are overtaking / climbing criteria met?
2 Typical Cross Sections
2A Are the lane widths, shoulders, medians and other cross section features in accordance with standard design and adequate for the function of the road?
2B Is the width of traffic lanes and roadway suitable in relation to:
- alignment?- traffic?- vehicle dimensions?- speed environment?- combinations of speed and traffic volume?
A collision diagram includes:
and crash information:
A condition diagram should include: