Thanks, tsuwm, for the explanation about slingshotting. (I knew I should double the t, but wondered if our non-native speakers of English would know what I meant if I did.) I was thinking it was different from threading the needle. Now, Jo, I've had a good lesson in British road systems, such as, that for your-all's biggest roads, the M stands for motorway. None of your motorways have more than two lanes in one direction?