Anyone traversing a conventional level crossing will experience a variation in warning times. Would it be possible to have consistent warning times? 

The warning time is the time from the red light at the crossing illuminates until the train is on the crossing. If you approach a level crossing the red light might be lit already. So, in this case, the perceived warning time will be shorter. But, always be careful when crossing, especially at unprotected crossings. 

A conventional level crossing warning time is calculated using the predetermined warning time for a given crossing and line speed. If all trains travel at line speed on approach to a level crossing the warning time will be consistent, which would mean the same warning time every time. However, this is not possible since trains travel at different speeds for a number of reasons. Hence this leads to varying warning times. 

The Network Rail type approved Wavetrain OMSL (PA05/06636) uses a different approach. Since the system uses acoustic signals in the rails to determine when to strike in, i.e., activate the warning measures, train speed or actual distance of the train is not relevant. In addition, varying train speed or type of rolling stock are interpreted differently. Hence, the warning time can to a certain extent be defined and made more consistent than conventional level crossing systems.