July 18, 2026 · Philip, Horus GPS
Your trucks idle 1,800 hours a year. Your kill switch may not know.
Here's a question almost nobody asks a tracking vendor: what does your kill switch do to an engine that's already running? For most of the market the honest answer is nothing — and for trucking, that's not a footnote. It's the whole story, because trucks idle for a living.
Trucks run when they're not driving
The U.S. Department of Energy puts long-haul truck idling at roughly 1,800 hours per year per truck — overnight heat in the winter, AC in the summer, reefer support, cold starts avoided. Plenty of drivers barely shut down between Monday and Friday.
That means the default state of an unattended tractor is often engine on. Any security device that only acts when the engine is off is protecting your trucks during the minority of their exposed hours.
What a starter interrupt actually does
The mainstream fleet immobilizer — including the add-ons from the big telematics platforms — is a relay spliced into the starter circuit. Send the command and the vehicle cannot be started next time. Samsara's documentation says it plainly: disable a vehicle while it's in motion and the immobilizer takes effect only after the vehicle stops and turns off.
Nothing about that design is dishonest — it's just built for vehicles that park and shut off every night. Cars, mostly.
The gap, in one scene
A tractor sits in the yard at 5 a.m., idling for heat, driver asleep in the bunk of a different unit or nobody around at all. Someone with an old key — or no key, since the engine's already running — climbs in, releases the brakes, and drives off. The starter interrupt on that truck never fires, because nobody asked the starter for anything.
The same logic covers the contractor who won't give a truck back: as long as he keeps it running or off your radar, a next-start blocker is a promise about some future morning, not control today.
What closes it
An active kill switch acts on the running engine. Once the vehicle is stationary — parked or idling — the owner shuts it down remotely and it stays down. Done right, it engages only when the vehicle is stationary; it will not stop a moving truck, because nothing responsible does.
That single difference re-covers the 1,800 idle hours a starter interrupt writes off — without touching the safety line every serious vendor agrees on.
Five questions to ask any vendor
Does your kill switch stop an engine that is already running, or only block the next start? What exactly happens if the truck is idling when I send the command? Is there any limit on how often I can use it? What extra hardware does immobilization require beyond the tracker itself? And what's the contract term if it doesn't work out?
Ask those five and the market sorts itself quickly. The comparison linked below walks the same questions across Samsara, Motive, Verizon Connect, consumer trackers, and Horus — with every claim cited to the vendor's own documentation.