The National Academies Press

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Pages 9-27

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From page 9... ... 1 Study Charge and Origin Roadside safety devices (including guardrails, break-away supports for signposts and roadway lights, median barriers, crash cushions, and other devices) are designed to reduce the risk of occupant injuries when a vehicle runs off the road. Read the entire page →
From page 10... ... 10 PERFORMANCE EVALUATION OF GUARDRAIL END TREATMENTS the occupants of a vehicle that strikes it. Highway agencies install end treatments of various designs. Read the entire page →
From page 11... ... STUDY CHARGE AND ORIGIN 11 • Develop a research design for evaluating the in-service crash performance of guardrail end treatments currently installed; • Determine the data required to carry out the analysis and examine data systems in selected states to determine whether the required data would be available; and • Identify appropriate next steps, which may include new data collection for evaluation or use of existing state data resources. The statement of task specifies that the committee is to develop a method for evaluating "the more common energy-absorbing W-beam guardrail end treatments currently installed." The committee anticipated that methods suitable for this specific category of devices also would be applicable for evaluating the safety performance of other kinds of roadside safety devices. Read the entire page →
From page 12... ... 12 PERFORMANCE EVALUATION OF GUARDRAIL END TREATMENTS of the study request, in particular, the past difficulties highway agencies have encountered in performing in-service evaluations of road features and concerns over the safety of certain guardrail end treatment designs. The committee also reviewed past evaluation studies as sources of examples of objectives, methodologies, and important practical constraints. Read the entire page →
From page 13... ... STUDY CHARGE AND ORIGIN 13 tures under real-world conditions. Differences between field performance and crash test results can arise due to many factors, including: • Field impact conditions that are not included in crash test guidelines, such as nontracking and side impacts; • Site conditions, such as roadside slopes and ditches, that adversely affect vehicle kinematics before, during, or after impact with the safety device; and • Sensitivity to installation details, such as soil resistance or barrier flare configuration. Read the entire page →
From page 14... ... 14 PERFORMANCE EVALUATION OF GUARDRAIL END TREATMENTS fied types (Joint AASHTO-FHWA Task Force on Guardrail Terminal Crash Analysis 2015, 23) Read the entire page →
From page 15... ... STUDY CHARGE AND ORIGIN 15 The evaluation based on this data would include the following: • Judgment of "whether the device performed as designed, and if not, whether there are extenuating circumstances"; • Identification of "problems identified with the construction, installation, and maintenance of the device and subsequent remedies"; and • "Recommended changes or modifications to the design and application of the feature." The term of the evaluation is suggested to be a maximum of 3 to 5 years, and pooling of efforts among several states is suggested to increase the number of devices and observed crashes. The continuous monitoring system would be a set of four spatially linked databases: • Highway geometric and traffic data, • Roadside feature inventory, • Maintenance records for roadside features, including records of crashes not reported to police, and • Crash data from police reports, with indication of the roadside devices involved. Read the entire page →
From page 16... ... 16 PERFORMANCE EVALUATION OF GUARDRAIL END TREATMENTS vide limited information relevant to assessing the performance of roadside safety devices. If a device performs as intended (i.e., preventing or reducing the severity of injuries in a crash in which the vehicle leaves the roadway) Read the entire page →
From page 17... ... STUDY CHARGE AND ORIGIN 17 In 2016, FHWA published the following summary of the work of the AASHTOFHWA Task Force (FHWA 2016) a: FHWA, in concert with the American Association of State Highway and Transportation Officials (AASHTO) Read the entire page →
From page 20... ... 20 T A B L E 1 -3 N um be rs o f C ra sh es i n W hi ch S tr ik in g a R oa ds id e O bj ec t W as t he M os t H ar m fu l E ve nt , Se le ct ed R oa ds id e O bj ec ts , an d A ll C ra sh es , 20 10 –2 01 5 Y ea r E nd T er m in al G ua rd ra il C on cr et e B ar ri er C ab le B ar ri er B ri dg e R ai l Im pa ct A tt en ua to r Si gn Su pp or t A ll C ra sh es 20 10 12 ,1 00 84 ,9 00 67 ,1 00 1 ,0 00 7, 80 0 2, 20 0 43 ,7 00 5, 41 9, 00 0 20 11 8 ,9 00 83 ,7 00 72 ,4 00 5 ,3 00 9, 80 0 3, 50 0 37 ,4 00 5, 33 8, 00 0 20 12 11 ,2 00 83 ,2 00 68 ,2 00 5 ,8 00 8, 30 0 3, 00 0 43 ,1 00 5, 61 5, 00 0 20 13 9 ,2 00 83 ,7 00 74 ,9 00 7 ,6 00 9, 20 0 2, 90 0 55 ,6 00 5, 68 7, 00 0 20 14 10 ,4 00 92 ,1 00 67 ,2 00 10 ,9 00 6, 80 0 2, 80 0 48 ,8 00 6, 06 4, 00 0 20 15 11 ,6 00 88 ,2 00 67 ,1 00 9 ,9 00 7, 30 0 2, 80 0 51 ,9 00 6, 29 6, 00 0 N O T E : T he N at io na l A ut om ot iv e Sa m pl in g Sy st em ( N A SS ) Read the entire page →
From page 21... ... STUDY CHARGE AND ORIGIN 21 designs now in use, and to meet common needs of the states and the federal government such as validation of crash testing, and • The routine in-service evaluation of end treatments and other roadside devices that MASH recommends for applications such as – Monitoring the highway agency's inventory of roadside devices to ensure proper condition, – Planning cost-effective maintenance and replacement, and – Checking that newly adopted devices are performing as expected. Two expert groups -- the AASHTO-FHWA Task Force that investigated guardrail end treatment crashes and the NCHRP project panel that prepared the project statement that was the origin of the present study -- recently identified a need for a research effort with national applicability to evaluate the in-service performance of roadside devices. Read the entire page →
From page 22... ... 22 PERFORMANCE EVALUATION OF GUARDRAIL END TREATMENTS The NCHRP project statement (NCHRP 2013) describes the evaluation envisioned as a research project to improve understanding of the performance of end treatments. Read the entire page →
From page 23... ... STUDY CHARGE AND ORIGIN 23 • Evaluation of the long-term performance of roadside safety devices with respect to safety and cost-effectiveness, as affected over time by maintenance and repair, normal deterioration, and changes in vehicle characteristics; and • Periodic evaluation of the agency's inventory of roadside safety devices to ensure that the devices installed are appropriate for their locations and that instances of improper installation or maintenance that can compromise performance are minimized. As noted above, the state highway agency interviews conducted for the committee, as well as earlier studies, found that highway agencies lack resources for conducting routine in-service evaluations. Read the entire page →
From page 24... ... 24 PERFORMANCE EVALUATION OF GUARDRAIL END TREATMENTS ficult in the highway construction environment -- and are not considered further in this report. Read the entire page →
From page 25... ... STUDY CHARGE AND ORIGIN 25 Practical considerations will dictate the choice of evaluation methods that highway agencies will be willing to adopt. The past studies summarized in Chapters 2 and 3 illustrate the difficulties of assembling timely and reliable data on the occurrence, circumstances, and outcome of crashes involving roadside safety devices; the locations, designs, and installation and maintenance history of the devices; and traffic and roadway characteristics in the study area. Read the entire page →
From page 26... ... 26 PERFORMANCE EVALUATION OF GUARDRAIL END TREATMENTS ORGANIZATION OF THE REPORT The remainder of this report is organized as follows: • Chapter 2 describes the methods used in past in-service evaluations of guardrail end treatments and other roadside safety devices. • Chapter 3 proposes objectives and procedures for a nationally coordinated research program for evaluation of roadside safety devices. Read the entire page →
From page 27... ... STUDY CHARGE AND ORIGIN 27 Joint AASHTO-FHWA Task Force on Guardrail Terminal Crash Analysis. Read the entire page →

From page 9...

... 1 Study Charge and Origin Roadside safety devices (including guardrails, break-away supports for signposts and roadway lights, median barriers, crash cushions, and other devices) are designed to reduce the risk of occupant injuries when a vehicle runs off the road.