The mytaxi implementation (on Android) doesn't seem to be sure whether cars have steering wheels or not. It's like Maggie Thatcher when it comes to U Turns. Hence it often gives clients ridiculous run in times so they cancel. On balance I reckon Hail0's straight line calculations, while technically inferior, were better in practice. In essence mytaxi's latest approach is overkill, trying to perfect something that can't be perfected given inherent communication delays, etc.