Report Containing Recommendations of the IRC Regional Workshops on Highway Safety
1984 Edition

IRC SP 27 advises several engineering approaches to enhance highway safety, including the removal or conspicuous marking of hazardous trees by painting them white with a black band for visibility. It recommends avoiding permanent distractions such as statues or constructions close to the roadway. For bridges and underpasses, the code suggests using advance warning signs, reflective painting on parapet ends, and guard rails or concrete barriers near piers and abutments to guide errant vehicles. At railway level crossings, it emphasizes maintaining clear sight triangles, removing obstructions, providing advance warning devices, and installing automatic signals or audio-visual alerts at unmanned crossings. For bus stops, locating them where visibility and grade are favorable, providing bus bays with drainage, and enforcing no-parking zones near them are recommended. Collectively, these measures aim to heighten visibility, eliminate hazards, regulate traffic flow, and ensure infrastructure safety.

The publication highlights that intersections account for a significant portion of road accidents, with risk increasing alongside intersection density. It identifies human factors such as driver perception and decision-making, and physical factors including the intersection geometry, visibility, and control devices. The code categorizes conflicts into less dangerous (merging, diverging, weaving) and more hazardous types (cutting maneuvers and right turns), prescribing design parameters such as small conflict angles, low relative speeds, adequate gaps, and priority controls to mitigate risk. Strategies include converting risky movements into safer weaving patterns via rotary designs, separating conflicting movements through signal timing or grade separation, and providing acceleration and deceleration lanes where appropriate. These measures collectively aim to reduce collision frequency and severity at intersections.

IRC SP 27 outlines that uncontrolled ribbon development causes local traffic congestion, pedestrian dangers, restricted sight lines, and driver distractions, exacerbated by roadside vendors and illegal parking near urban areas. To counter these issues, it recommends constructing parallel service roads to segregate local and slow-moving traffic, installing railing barriers, and maintaining footpaths to encourage pedestrian safety. The document advises providing off-road truck parks for rest and vehicle maintenance, enforcing no-parking zones on main carriageways, and situating bus stops in lay-byes or off-road terminals. It also stresses regulating the location and frequency of fuel stations and consolidating check barriers to avoid excessive proliferation. Approaches to cities should feature widened roads with adequate footpaths, cycle tracks, and service roads, supported by railing barriers for pedestrian protection. These guidelines serve to improve safety and traffic flow by controlling roadside land use and access.

The standard emphasizes that adequate sight distance is crucial for safe vehicle operation, encompassing stopping, overtaking, and maneuvering. It recommends providing at least intermediate sight distance on two-lane highways and designing vertical curves to ensure visibility for stopping and overtaking. Horizontal curves should have obstructions cut back to improve lateral visibility. Roadside clearance of at least 1.5 meters free from obstructions is advised to enhance driver confidence. Medians are recommended on rural highways with four or more lanes and urban roads with six or more lanes to reduce glare and separate traffic streams, with limited median openings spaced at minimum distances of 750 meters in rural areas and 500 meters in urban arterials. Embankment slopes should be gentle (4:1 for embankments up to 1.5 meters, with steeper slopes transitioning to flatter ones for higher embankments) to facilitate vehicle recovery. Hard shoulders at least 1 meter wide are recommended, avoiding high or low shoulders that cause water pooling or pavement edge breakage. Intersection locations should favor straight alignments and near-level grades with adequate sight triangles and channelization to minimize conflicts.

IRC SP 27 underscores the importance of both enforcement and education in fostering safer roads. Enforcement involves applying and upholding speed limits appropriate for traffic conditions, regulating parking especially in congested and public areas, ensuring vehicle compliance with weight and dimension standards, conducting fitness inspections to remove unfit vehicles, and overseeing driver licensing and behavior regulations, including mandatory safety equipment like helmets and seat belts. It also involves imposing penalties and strengthening enforcement personnel capabilities with technological tools. Education complements enforcement by increasing public awareness about traffic laws, promoting the consistent use of safety gear, and encouraging responsible driving practices to reduce accidents. Together, these elements create a comprehensive framework that combines legal compliance with behavioral change to improve traffic safety.