Star rating designs

Apart from assessing existing roads, Star Ratings are being used to ensure that safety is built-in to designs for major upgrades and new roads prior to construction.

It is critically important that people’s safety and well-being is not overlooked in favour of more traditional objectives such as reducing congestion and travel times. The seven major multilateral development banks are improving safety performance measures for the road designs they finance.  Similarly, the Commission for Global Road Safety recommends that desired design speeds for new roads should be subject to achieving minimum safety ratings.

The Karnataka State Highway Improvement Project (KSHIP) in India provides a good example of how Star Ratings are being used to design safer roads:

1. The World Bank initially set a target of three-stars for road safety demonstration corridors.  The Government then extended this target to include around 500km of additional roads.
2. With funding support from the Global Road Safety Facility and Bloomberg Philanthropies, road safety inspections were carried out and baseline Star Ratings calculated for the existing roads.
3. Consulting engineers and road authority engineers used Star Ratings to test the safety impact of various design options, such as ‘raised pedestrian crossings’.
4. Final designs were based on optimised Star Ratings and met local design standards and budget and environmental requirements. 

This process resulted in designs with significantly better Star Ratings than the existing roads. For example, the percentage of road rated one-star or two-stars for vehicle occupants reduced from 86% to 2%. It was estimated that the new designs would result in 55% fewer deaths and serious injuries than currently occur.

A project in the Republic of Moldova produced similarly impressive results. With the support of the MCC, the Global Road Safety Facility and engineers from URS Corporation and Universinj, designs that particularly focused on pedestrians in villages increased the percentage of road rated four-stars from 8% to 84%. Final designs were estimated to reduce risk of deaths and serious injuries by 40%.

Safety inspections

By systematically inspecting roads, countries can develop an understanding of the level of risk that is ‘built in’ to their road networks.  This provides a basis for targeting high-risk sections of road for improvement before people are killed or seriously injured. Inspections are especially useful when crash data is unavailable or unreliable.

iRAP inspections use specially equipped vehicles to collect digital, panoramic images or videos of roads. These images are then used to record (or ‘code’) road design attributes that are known to influence the likelihood of a crash and its severity. The inspections create a permanent video and database record that can be reviewed easily by local engineers and planners. 

The attributes, which are recorded at 100 metre intervals, include: 

• traffic speeds
• number of lanes
• lane width
• motorcycle facilities
• paved shoulder width 
• audio-tactile lines
• median type
• curvature and curve quality
• roadside design/obstacle
• delineation
• pavement condition 
• overtaking demand
• intersection layout, volume and quality
• minor access point density
• bicycle facilities 
• pedestrian crossing facilities and quality
• sidewalk provision
• side friction/roadside activities.

Countries do not need to inspect every road in order to make a large difference; in India, about two-thirds of deaths occur on state and national highways which account for just 6% of the network.

iRAP encourages countries to focus inspections on their busiest roads, where the largest safety gains can be made. In Mexico, for example, assessments cover around 45,000km of federal roads, which is a little more than 10% of the nation’s roads (and around one third of paved roads).

To enable the cost-effective assessment of roads, there is a global network of accredited suppliers who are capable of competitively bidding to undertake high-quality inspections and coding.  

Star ratings

Star Ratings are an objective measure of the likelihood of a crash occurring and its severity. They draw on road safety inspection data and the extensive real-world relationships between road attributes and crash rates.

Research shows that a person’s risk of death or serious injury is highest on a one-star road and lowest on a five-star road.

By measuring the risk associated with road attributes, Star Ratings can provide a better indicator of the influence of road attributes on risk than crash numbers alone. The focus of Star Ratings is on attributes that influence the most common and severe types of crashes for vehicle occupants, motorcyclists, pedestrians and bicyclists. 

The charts below help to explain why low-income and middle-income countries experience such high rates of death and serious injury. In total, some 50,000km of roads in low-income and middle income countries have been Star Rated. Significant proportions of the roads are rated just one-star or two-stars.

The road safety inspections and Star Ratings provide countries and international finance institutions with a set of highly objective indicators that can be used in setting ambitious road safety targets. National targets have been shown to play an important role in altering the community’s view of the inevitability of road trauma and driving action to save lives. The Netherlands, for example, has committed to bring all one-star and two-star roads up to at least three-stars, while New Zealand is ensuring that all Roads of National Significance will be at least four-stars.

The assessments of some 50,000km of roads in low-income and middle-income countries found that many of the roads assessed to date lack the most basic engineering safety features such as footpaths, safety barriers, paved shoulders and safe intersection design. The risk factors on this page play a significant role in the Star Rating results and provide a basis for planning life-saving treatments.