Alcohol interlock: breathalyser and GPS tracker

Each driver is issued his own RFID card with a factory 64-bit number. The 1-Wire reader is fitted in the cab and the breathalyser next to it, within easy reach from the driver's seat. The breathalyser can be powered from a cigarette lighter adapter. The starter circuit is routed through an output of the tracker and works on the immobiliser scenario.

How the driver's morning goes. He gets into the vehicle and presents his card to the reader. The tracker recognises who it is. If the card is his own and permitted, the next step is the breathalyser: the driver blows into a reusable mouthpiece and the instrument returns a result within seconds. No alcohol found, and the tracker releases the starter, logs a start-of-shift event with the date and time, and the vehicle starts. Alcohol found, and the starter stays locked while an alert goes to the server. From there the driver follows the company's internal procedure: rings his manager, waits for a replacement, goes for a medical examination.

If even one step fails — someone else's card, or a positive test — the vehicle will not move. The manager or the person responsible for safety sees all these events in the monitoring system in real time and in reports.

At the end of the shift the driver presents his card again. The tracker logs an end-of-shift event and the ignition can be switched off. So the interlock turns into working-time recording of its own accord: who worked, on which vehicle, and from when to when.

About the breathalyser itself. The Alcovisor Mercury uses an electrochemical fuel cell: alcohol in the breath sample produces a voltage across the cell in proportion to its concentration, and the instrument converts that into blood alcohol content. The model has two modes. The screening, or passive, mode answers the question of whether there is alcohol or not and works with a reusable mouthpiece. The standard, or active, mode gives an exact figure and requires a disposable mouthpiece. For a daily interlock the Teltonika example uses the screening test: it is faster and does not need a consumable for every check.

Configuration. In the Teltonika configurator the breathalyser check function is enabled on the FMC125 in the immobiliser section. The RS232 port mode is then set for working with the Mercury breathalyser. Electrically, the TXD and GND pins of the breathalyser's USB connector are joined to the RXD and GND pins of the tracker's RS232 port. Before going live the breathalyser is calibrated to the manufacturer's instructions, and calibration is then repeated at the interval the manufacturer specifies.

Who this suits. Almost any fleet of cars and light commercial vehicles where the driver works unsupervised: internet and cable providers, utilities, the postal service, sanitation services, construction, manufacturing, retail and wholesale trade.

The interlock does not replace the rest of the monitoring. With an LV-CAN200 adapter the FMC125 reads CAN bus data, and built-in scenarios log driving style, speeding, long idling, towing, crashes, trips and automatic geofences. From mileage and engine hours the system gives service reminders, so vehicles do not go out with maintenance overdue.

Tracker firmware and configuration are updated remotely through FOTA WEB. If the company changes the rules — adding new drivers, say, or altering how the lockout works — there is no need to go round the vehicles.

An episode from the life of such a fleet. Friday, 7:40, and a provider's service engineer gets into the vehicle assigned to him outside his house. The card is accepted, the test finds alcohol — a friend's birthday the evening before. The starter does not engage, and the safety officer receives a notification with the driver's name, the vehicle number and the address. He rings the engineer, the morning's jobs are handed to a colleague, and the engineer himself starts work later, after a second test. Without the interlock this man would have driven right across town to his first call, and most likely nobody would ever have known. Or they would have known — but only after a crash.

Common questions. Can the instrument be fooled by somebody blowing on the driver's behalf? The card is tied to a person, but physically a passenger can blow into it too; that is why some companies also fit a camera in the cab that takes a still at the moment of the test. What if the driver drinks in the middle of the shift? The arrangement in the example tests the person at engine start, so rules for retesting — after a long stop, for instance — are set separately in the configuration and in the internal procedure. Does the interlock work with no mobile coverage? Yes: the decision to allow starting is taken by the tracker in the vehicle, and the events go to the server once the network appears.

Why not simply a pre-trip medical check. The medical check stays where it is required, but it happens once, in one place. The interlock tests the driver where the vehicle actually starts, and every time, not only on a Monday morning when the medic is on site.