Vehicle in-use tyre characteristics evaluation during winter driving training
Riga Technical University, Faculty of Mechanical Engineering, Transport and Aeronautics, Department of Automotive Engineering, 6k Ezermalas street, LV1006 Riga, Latvia
After the substantial number of fatalities in road traffic increase with the start of icy 2014–2015 winter conditions in Latvia drivers have been offered complimentary winter driving training. Having numerous drivers with their cars performing the same braking actions on restricted and safe test ground gave a good opportunity for evaluating driver skills and vehicle in-use tyre condition. Tyre age and tread depth were measured and driving instructions have been given to more than a thousand participants. Instrumented braking and manoeuvring measurements were made for thirty cars. The equipment included GPS receiver and decelerometer. Measurement results have been compared against physical observations and hints given by professional driving instructors. The comparison indicated that although the suggestions given to drivers by professional instructors clearly contribute to safer driving, the visual evaluation without measuring may lead to various errors in messages conveyed to drivers. The most questionable statement was about the influence of the vehicle mass on braking distance. The investigation did not show essential vehicle mass influence on tyre grip and correspondingly on braking characteristics. Tyre tread depth effect on braking performance demonstrated the relevance of technical requirements for winter tyres. The advantage of using public training for winter tyre in-use experiments is lower cost for getting tyre samples with various technical conditions. The disadvantages are the different skills of car owners, the need for individual instructions and the necessity to reckon with the training format, the limited choice of the testing variables and substandard conditioning of the road surface. The tests gave valuable information for further training sessions and coming winter tyre tests.