Traditional school of Vastu thoughts forbids traveling in wrong direction on certain days, for instance traveling westwards on Tuesday is considered inauspicious and is not recommended. Likewise going towards North on Saturday or down South Sunday is not suggested in Vastu. These old school thoughts of Vastu are being not followed by everyone that are based on astrological grounds in which ruling planet of the day is the deciding factor for corresponding direction of specific day.
It is believed that going westwards on Sunday whose ruling Lord is Sun governs over East, is like going against the Lord. Traveling opposite the certain day's direction is not in consonance to the energies of the day. Some people may not find it authentic but such thoughts are still valid and accepted as old customs imbibed from ancient books. They are applicable today but in a different mannerism which makes possible our work traveling in certain direction on any day.
The measure that one can take to avoid going against the specific day's Lord is to travel hundred yards or to have a look towards the favourable direction, then turn back to path. This is as easy and simple as anything!