SPIs on Protective Systems

Introduction

International or regional comparisons of protective systems' use rates are vital tools for recognising deficiencies, setting priorities and stimulating efforts at the political level.

The major protective systems in vehicles that are relevant for the development of SPIs are seat belts for adults and for children, in various types of vehicles and the use of

safety helmets by cyclists, moped riders and motorcyclists. The SPIs developed are:

Set I: Daytime wearing rates of seat belts

SPI A – Front seats – passenger cars + vans /under 3.5 tons/

SPI B – Rear seats – passenger cars + vans /under 3.5 tons/

SPI C – Children under 12 years old - restraint systems use in passenger cars

SPI D – Front seats – HGV + coaches /above 3.5 tons/

Set II: Daytime usage rates of safety helmets

SPI F – Cyclists

SPI G – Moped riders

SPI H – Motorcyclists

Read more about SPIs for protective systems in the report Safety Performance Indicators: Theory

Measurement methods

The SPI Manual explains aggregation of SPI protective systems data for road types, for different regions, for driver and front seat passengers, for different age groups, and explains how development over time can be calculated. The SPI Manual presents several guidelines for measurement of SPIs on protective systems, for example:

• The sample identified for the survey should have a probability-based design such that estimates of safety belt (helmets) use will be representative for the population of interest in the country and confidence intervals may be calculated for each estimate produced.
• The SPI values should be assessed on all major road types and relevant for each road user category. The target population for each of SPI category encompasses all national (regional) citizens as well as all foreigners in traffic.
• Observation sites must be randomly assigned to the selected day-of week/ time of-day time slots. Only in case of use of restraints by children, the observations should be carried out on weekend days.
• Observation (registration) should be performed on road profiles, intersections, petrol stations or other eligible locations such as in the vicinity of shopping centres. (Automatic) video devices can be used as well. The observation of seat belt use in coaches should be performed by an observer who is present on-board during a journey.
• The observations should be performed by independent observers (not uniformed police or other officers) working under the responsibility of a survey coordinator, assuring that wearing rates would be not influenced.
• Observers shall be required to follow a predetermined, clear policy in the event that observations cannot be made at the assigned site at the specified time (due to heavy rain, construction, safety problems, etc.).
• As a rule of thumb, between 20 and 30 observation sites suffice for most SPI’s on protective systems. For one SPI, belt use by passenger car and vans occupants over 12 years old in front seats, it is recommended that at least 30 observation sites are used.
• As a rule of thumb, between 50 and 100 observations per observation site suffice. For two SPIs, (1) belt use bypassenger car and vans occupants over 12 years old in front seats and (2) belt use by passenger car and vans occupants over 12 years old in rear seats, it is recommended that at least 100 observations per site are collected.

Recommendations

It is recommended to use the SPIs proposed for protective systems to measure the effects of interventions and to calculate social costs of prevented accidents as well as a reduction potential.

behind the increased rates. Measuring protective systems' use by road users allows estimation of not only fatalities' and serious injuries' reduction due to their use, but also estimation of reduction potential by their increased use. This in turns allows one to perform cost benefit analyses of relevant road safety measures.