Most "new" cars handbrakes work very well and will hold on a "steepish" gradient but only if they are serviced properly. The main problem with poor handbrakes (assuming they are designed correctly) is the auto adjusting mechanism on the pads or shoes not working as it should or seized up so the leverage points are all wrong. Cowboy mechanics adjusting handbrake cables don't help this, and I would like a quid for everytime that I've slackened a cable off and let the adjusters work and BINGO. The UK MOT standards only require 16% on dual circuit brakes and 25% on single circuits and can differ from side to side as long as they reach the required % together. However after saying all that some handbrakes are rubbish compared to others and have a job to "scrape" through a test even when everthing is renewed.
