Road safety effects due to adaptation of the time intervals of periodic vehicle inspection (MOT) : the same time schedule for Diesel/LPG (3-1) and Gasoline/Electric (4-2-2-1) vehicles. All light motor vehicles in the Netherlands are subjected to regular periodic vehicle inspections (MOT), the time intervals being determined by fuel type and age of the vehicle. Diesel and LPG cars (DG group) must undergo their first inspection after three years at the latest, followed by annual inspections. This is called the 3-1 frequency pattern. Petrol and electric cars (BE-group) must now be tested for the first time after a maximum of four years, undergo biennial inspections during the next four years, followed by annual inspections. This is known as the 4-2-2-1 frequency pattern. SWOV investigated if and how a different MOT frequency will affect the expected number of road fatalities in 2013. This was done for four different frequency patterns. In addition, the effect was investigated of the additional rule that cars with a distance travelled exceeding 160 000 km must undergo annual inspections; the 160 000+ rule. The study showed that in each of the eight different variants safety is affected, but the effects vary. The 160 000+ rule was also investigated when applied to the present frequency pattern. The table shown in the summary presents the safety effects of the different frequency patterns expressed by the additional number of road fatalities as compared to the present frequency pattern. The largest increase (+11.3 fatalities) has the effect of a relative 2.8% increase in the total number of road fatalities in crashes involving a passenger car or van. This has the effect of a 2.0% increase in the total number of road fatalities. The effects are the result of a more frequent testing of vehicles in the BEgroup and the less frequent testing of vehicles in the DG-group; the latter of the two effects being stronger. Vehicles in which rejection points are found that are repaired during inspection, return to the road without these rejection points. If, according to the frequency pattern, these vehicle were to be tested one year later, SWOV assumes that the vehicles drive a whole extra year with these rejection points. If cars with high distance travelled were to be inspected more frequently, this effect will be undone again for these cars. The results therefore indicate that the 160 000+ rule will lead to a considerable decrease of the calculated number of additional road fatalities. The analysis was carried out by fuel type on the basis of data of cars that passed and cars that failed the inspection, the rejection points, their age and their mileage; this data was provided by provided by RDW, Vehicle Technology and Information Centre. In addition, data was used provided by Statistics Netherlands about the distance travelled by cars and vans by age. In the analysis the annual distance travelled was calculated with a rejection point Dg for both the presently used frequency patterns (3-1 and 4-2-2-1) and for the nine alternative frequency patterns. Crash data and literature about crashes resulting from technical defects were used as a basis to determine the additional risk due to technical defects. For cars and vans this additional risk was added to the “normal risk” of a fatal crash for these vehicles. This “normal risk” refers to crashes in which other factors (e.g. alcohol, distraction, et cetera) played a role. In the Netherlands, the “normal risk” of a fatal crash for a car occupant or a vulnerable road user who is hit by a van or car is approximately 2.8 ? 10-9 fatalities/km. This study determined the additional risk attributable to technical defects to be 1.8 fatalities per 109 km travelled. The results in this report were obtained by determining the additional distance travelled with the defects and multiply this distance with the additional risk.
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