Road Safety Engineering
Road safety audits are systematic examinations of roadway projects to identify potential safety issues. The audit is conducted by an independent team of safety specialists who review the project plans and field conditions. The audit identifies the safety concerns and recommends design modifications to reduce crash risk. The crash analysis uses historical crash data to identify high-crash locations and crash patterns. The crash frequency, crash rate, and crash severity are analyzed to prioritize locations for safety improvements. The safety performance functions predict the expected crash frequency for a roadway based on its traffic volume and geometric characteristics. The empirical Bayes method combines the predicted crash frequency from the SPF with the observed crash history to estimate the expected crash frequency. The highway safety manual provides the standard methodology for roadway safety analysis in the United States.
The selection of safety countermeasures is based on the identified crash patterns and the proven effectiveness of each countermeasure. The countermeasure effectiveness is expressed as a crash modification factor that represents the expected percent change in crashes after the countermeasure is implemented. The installation of roundabouts at intersections reduces severe crashes by 75 percent. The addition of left-turn lanes at intersections reduces crashes by 25 to 50 percent. The installation of roadside barriers reduces the severity of run-off-road crashes. The rumble strips on roadway shoulders alert drivers who are leaving the travel lane. The safety improvements are prioritized using benefit-cost analysis to achieve the maximum safety benefit for the available funding.
Road Safety Data Analysis
The systematic collection and analysis of crash data is essential for identifying safety problems and evaluating the effectiveness of countermeasures. The state Departments of Transportation maintain crash databases that record the location, severity, type, and contributing factors for each reported crash. The geographic information system mapping of crash locations identifies high-crash intersections and corridor segments. The crash clustering analysis identifies locations where crashes are concentrated and where safety improvements are most needed. The empirical Bayes method combines the observed crash history with the predicted crash frequency from safety performance functions to estimate the expected crash frequency. The EB method accounts for the regression-to-the-mean bias that occurs when sites are selected for treatment based on a short-term spike in crashes. The cross-sectional and before-after studies evaluate the effectiveness of safety countermeasures by comparing crash frequencies before and after implementation, with appropriate adjustments for traffic volume changes and crash trends.
The Highway Safety Manual provides a standardized methodology for roadway safety analysis that is used by transportation agencies across the United States. The Part C predictive method estimates the expected crash frequency for a roadway facility based on its geometric design features and traffic volumes. The crash modification factors from the HSM and other research studies quantify the safety effect of specific countermeasures. The economic analysis of safety improvements uses the crash reduction benefits and the construction costs to calculate the benefit-cost ratio and the net present value. The safety management process identifies sites with potential for safety improvement, diagnoses the crash patterns, selects countermeasures, prioritizes projects, and evaluates the safety effectiveness of the implemented improvements.
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Quality Control and Inspection
The quality control program for any construction activity includes the inspection of materials upon delivery, the observation of work in progress, and the testing of completed work. The inspector verifies that the materials meet the specifications and are stored properly to prevent damage before installation. The observation of the work during installation identifies any deviations from the contract documents that must be corrected before the work is concealed by subsequent construction. The testing of the completed work verifies that the installed materials achieve the specified performance requirements for strength, durability, and function. The documentation of the inspection and testing results provides the permanent record of quality for the project that is used for future maintenance and renovation. The non-conformance report documents any work that fails to meet the specifications and tracks the corrective action through to completion and verification.
The quality assurance program provides confidence that the quality control activities are being performed effectively. The QA program includes audits of the QC processes, review of the documentation, and independent verification of the test results. The QA manager reports to senior management independently of the project management to ensure objective evaluation of quality. The QA program also includes the training and qualification of the inspection and testing personnel. The corrective action process identifies the root cause of quality problems and implements changes to prevent recurrence. The continuous improvement of the quality program uses the feedback from the QC and QA activities to improve the processes and procedures for future projects.
Codes and Standards Compliance
The building code requirements for each type of construction are established by the International Codes and the applicable local amendments. The designer must review the code requirements for the specific occupancy and type of construction to ensure that the design complies with all applicable provisions. The fire resistance requirements, structural loading criteria, energy efficiency standards, and accessibility provisions must all be addressed in the design. The special inspections required by the building code for seismic and wind resistance must be performed by qualified inspectors. The documentation of code compliance includes the plans, specifications, calculations, and test reports that demonstrate that the construction meets the code requirements. The permit application review by the building department verifies that the design complies with the code before construction begins.
The industry standards published by ASTM, ANSI, ACI, AISC, and other organizations provide the material specifications and test methods referenced by the building codes. The ASTM standards cover the testing and specification of construction materials including concrete, steel, masonry, and wood. The ACI standards provide the code requirements and design guidance for concrete structures. The AISC specification governs the design of steel structures. The MSJC code provides the requirements for masonry structures. The reference to these standards in the contract documents ensures that the materials and workmanship meet the established industry benchmarks for quality and performance.
Environmental Considerations
The environmental impact of construction activities must be managed to comply with regulations and to minimize the effect on the surrounding community. The stormwater pollution prevention plan for construction sites controls erosion and sediment runoff during the construction period. The dust control measures including water spraying, wind barriers, and stabilizing exposed soils prevent air quality impacts. The noise control measures limit construction activities to permitted hours and use quieter equipment where feasible. The waste management plan diverts construction and demolition waste from landfills through recycling and reuse. The material storage and handling procedures prevent spills of fuels, oils, and other hazardous materials that could contaminate the soil and groundwater. The site restoration after construction includes revegetation, landscaping, and the removal of temporary facilities to return the site to its intended final condition.
The sustainable construction practices reduce the environmental footprint of the project through material selection, waste reduction, and energy-efficient construction methods. The use of locally sourced materials reduces transportation energy. The recycling of construction waste including concrete, steel, wood, and cardboard reduces landfill disposal. The construction of energy-efficient buildings reduces the operational energy consumption and greenhouse gas emissions over the building life. The indoor air quality during construction is protected by sequencing the work to avoid contamination and by ventilating the building before occupancy.