As mentioned in the call loop post, although call loops are used on almost all of the alignment, most of Burnside does not use them. Instead, on Burnside you will find mass detectors.
These look a little similar to call loops, but they’re smaller and they function differently. While a call loop requires interaction from the operator to select a signal, a mass detector works automatically when a train passes over it. The mass detector detects the mass of the train (I love the things that are intuitively named) which will automatically call the pre-empt and bring it up when the train reaches the intersection – no button pressing on the part of the operator is required.
Most of Burnside works on mass detection rather than call loops, but that only works when the train is running normal traffic (east in the eastbound and west in the westbound). There aren’t mass detectors set up for trains running reverse traffic (west in the eastbound or east in the westbound) so operators have to call Control for permission to get through the intersections (aka SOP the intersection) if they are running reverse.
Mass detectors can also be found elsewhere in the alignment, such as at 12th & Washington westbound, where the mass detector will automatically bring the crossing gates down when a train arrives at the platform.