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What is the SRF Vehicle Detector?

The SRF vehicle detector uses sonar to detect vehicle presence

Fleetwatch FMS · Fuel Lane Hardware
The SRF55 Vehicle Detector: How It Works
The SRF55 is an overhead vehicle detector that uses sonar to sense when a bus is in the fueling lane. When the bus drives out from underneath it, the SRF55 sends a reset signal to the RIH, which closes the transaction and returns the RIH to the Employee prompt for the next vehicle.

How It Works

Bus pulls in
SRF55 senses the roof
 → Bus is fueled
transaction stays open
 → Bus drives away
reset signal sent to the RIH
Fleetwatch parking diagram showing a bus parked under the SRF55 vehicle detector beside the RIH and a diesel dispenser
The SRF55 in the fuel lane with the RIH and diesel dispenser. While the bus is fueled, the SRF55 senses its roof. Park under the detector during servicing to avoid an unintentional reset.

Quick Troubleshooting at the JB20

The SRF55 connects to a control module (the “black box”) wired into the JB20 junction box. Its green LED tells you what the detector is doing:

Off Normal. No vehicle under the sensor.
On steady Normal. A vehicle is under the sensor.
Flashing Problem. The black box and the overhead sensor aren’t communicating. Check the wiring between them.
Quick troubleshooting guide showing the SRF55 black box and green LED, the vehicle detector terminal block, I/O block terminals 23 and 25, and the wiring table
Quick troubleshooting guide: how the SRF55 connects in the JB20, how the green LED should behave, and the wiring for each terminal.
For step-by-step troubleshooting and the full wiring table, see Checking the SRF55 Vehicle Detector. If resets happen mid-fueling, see Vehicle Detector Resets While Fueling.

Placing the SRF55 for a Mixed Fleet

When a fleet has buses and vehicles of different sizes, they don’t all stop in exactly the same place. The SRF55 is mounted over the vehicle centerline at the center of the common overlap between all vehicle types in their service positions, so every type is detected while it’s being fueled.

Elevation and plan view drawings showing the SRF55 mounted over the vehicle centerline, at the approximate center of the common overlap between four vehicle types in their service positions
Elevation (left) and plan view (right). Each vehicle type stops in its service position, and the SRF55 sits where all of them overlap.
Planning a new installation
• The exact location of the SRF55 is usually set near project completion, when buses are available to help with placement.
• For advance placement (before construction), S&A Systems needs a scaled drawing showing exactly where each bus type in the fleet stops while fueling.

Meet the SRF55

An SRF55 vehicle detector with its cable and connectors
An SRF55 at the factory, waiting to ship to a customer site!
Questions about the SRF55 or placing one in your fuel lane? Contact Fleetwatch Support.