TRL Ltd. performed an assessment of the durability and reliability of typical hydraulically operated parking brakes fitted to three previously used quadricycles in accordance with the requirements as laid down in paragraphs 2.3 and 2.4 of Directive 93/14/EEC. When tested with the parking brake applied sufficiently to hold the quadricycle stationary on the gradient all three vehicles failed the test. When a force of 400N was applied to the handbrake lever two of the three quadricycles passed the test. However, both vehicles exhibited a trend for the parking brake system pressure to decay. The other vehicle failed the test. These results show that the method of using the energy stored in a hydraulic system to provide the parking brake function has not proved reliable.

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