Road safety audit on a major freeway: implementing safety improvements

Vardaki, Sophia; Papadimitriou, Fanis; Kopelias, Pantelis · 2014 · OpenAlex-citations

DOI: 10.1007/s12544-014-0138-0

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Summary

This paper details the methodology, findings, and implementation of a Road Safety Audit (RSA) conducted on the Attica Freeway (“Attiki Odos”), a 70 km urban ring road in Athens, Greece. The study was motivated by the need to improve safety levels on a newly constructed freeway that, despite high design quality, faced challenges related to high operating speeds, increasing traffic volumes, and a disproportionately high rate of motorcycle crashes. The RSA aimed to identify dangerous roadway features and misleading information by applying principles of positive guidance and self-explaining roads, while also proposing pilot treatments for broader application. The RSA was performed in 2009 by an independent, multidisciplinary team of experienced road safety engineers. The process followed a formalized structure: the operator selected the team, designers provided project data, and a pre-audit meeting established context. The audit team reviewed design standards, traffic volumes, alignment plans, crash data, and previous audit reports. Field inspections were conducted during daylight and nighttime, in both wet and dry conditions, to assess driver perception and expectancy violations. The audit specifically considered vulnerable road users, including motorcyclists and older drivers, utilizing data from prior performance assessment studies. The audit identified several critical safety issues, categorized into signage, roadside hazards, cross-sections, sight distances, and driver behavior. Key findings included faded or old road markings, unprotected roadside equipment (such as lighting columns and bridge abutments), variable emergency lane widths, and limited stopping and decision sight distances at complex maneuvers like freeway splits and tunnel exits. The team recommended specific countermeasures, including the installation of roadside barriers to fill gaps, constant emergency lane widths, elimination of vegetation restricting visibility, and improved skid resistance. Special attention was given to motorcyclists, recommending the addition of “skirting” to restraint systems on tight curves. Following the audit, the freeway operator promptly implemented several recommendations. These included using shot blasting to remove old markings and improve skid resistance, installing automatic speed cameras at 14 sites, adding skirting to restraint systems, and enhancing signage and delineation. A before-and-after analysis of the shot blasting interventions showed significant improvements in skid resistance (Grip Number values) and a statistically significant reduction in crashes ($\chi^2 = 42, p<0.01$). Additionally, the installation of speed cameras resulted in a 4% reduction in average speeds. The study concludes that the RSA effectively promoted the implementation of innovative safety measures, such as shot blasting and motorcyclist-friendly restraints, and highlights the importance of proactive safety assessments in maintaining safe freeway operations.

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• adas effectiveness

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• Applied Guidance: countermeasure evaluation
• Empirical Findings: crash risk outcomes