Changes

Take the metro line B (yellow) to the last station, Cerny Most, then continue in the same direction. About 10 minutes down the road there is a highway bridge. Pass under it and turn right to get on the highway. Continue until you reach the railway bridge and hitch just before it . The problem is, that people don't usually go that way if they are going north. You can also get to an easily reachable gas station on the highway getting north walking.You must go to Letňanská (e.g. bus 186 or 233 from Palmovka). Then going down from the bus, you can see the entrance of the highway straight ahead. Put yourself so you have the highway on your right, then cross the street (going north then), and then the parkings, and go behing the buildings, looking for a small bridge ("most" in czech), going above the highway. From there you will see first mapthe gas station. There are not so many people stopping there, but they all are (almost) going in the good direction. Just ask if they are going north ("sever") or if they can just let you on the next gas station ("došla pumpa"/"doshla pumpa"), where there will be normally more cars.