For Timers who use two timing devices at a location, which is a common practice at start and finish lines for higher density races, it can be confusing to see the option to assign a Stream as a Main or Backup. Any times that come into Streams that are assigned as a Backup Stream on a Timing Location will only be considered if there is not an instance of that bib or chip passing on a Main Stream assigned to the same Location. This example will detail out why we give the guidance of assigning all chip streams as Main streams on the same location, even if you have one set further back as a redundancy.

For the example below, we will use a finish line setup with two rows of mats. The first line of mats the participant would cross (the one right on the finish line) will be called Primary and the second line crossed, the one that is a redundancy, will be called Secondary.

Let's say we assign the Primary stream as a Main stream and the Secondary stream as a Backup stream for the finish:

Now, if a participant finishes the race and doesn't read on the Primary stream (say they covered their bib stopping their watch, the most common reason) but is picked up on the Secondary stream at 9:30am you can see that we will use that read, as there is not a valid read on the Main stream:

This is generally fine, however if that participant comes back into the finish area for some reason and reads on the Primary stream at 9:45am that read would meet the conditions to be used and since there isn't a valid read on a Main stream already RaceDay Scoring will use the 9:45am read and not the 9:30am read:

This will change Gordon Bombay's time and make it 15 minutes later than his actual finish.

If both the Primary and Secondary streams had been set as Main streams this would have been avoided, as the Finish location is only expecting a single occurrence in this scenario and therefore the 9:45am read would not be used: