Sat-nav woes

I really should have learnt by now to stop trusting the sat-nav, particularly with regard to the traffic updates which don’t seem to be particularly accurate. Today, the sat-nav diverted me off the main road (which seemed perfectly clear as far as I could see) straight into a huge traffic jam thus making my journey considerably slower than I suspect it would have been had I ignored it and continued with the original route. Fortunately I was running ahead of schedule and so still managed to get to my appointment on time, despite the traffic, but it was very frustrating.