Since December 2017, almost all CDL drivers operating in interstate commerce are required to use a registered Electronic Logging Device (ELD) to record their hours of service. The device automatically records driving time by connecting to the truck's engine, replacing the paper logbooks that were standard for decades.
What an ELD does
An ELD records: driving time (automatic, based on vehicle motion); date and time of all duty status changes; current location; engine hours and miles; vehicle and driver identifying information. The ELD is connected to the truck's engine control module (ECM) so it can detect movement automatically — you cannot "log off" while the truck is rolling.
Who must use an ELD
Any driver required to keep records of duty status (RODS) under 49 CFR Part 395 — which covers virtually every interstate CDL driver. The driver, not the carrier, is responsible for compliance. The ELD must be on the FMCSA's Registered ELD list.
Exemptions
Drivers who use the short-haul exception (return to base within 14 hours, 150 air-mile radius); drivers operating vehicles older than model year 2000 (no ECM available); drivers in driveaway-towaway operations where the vehicle being driven is the cargo; and drivers who only have to keep RODS for 8 days or fewer in any 30-day period are all exempt.
If your ELD malfunctions
You're required to: notify your carrier in writing within 24 hours; reconstruct duty-status records for the current 24-hour period and the previous 7 days using paper logs; continue keeping paper logs until the ELD is repaired or replaced (the carrier has 8 days to repair or 8 days to obtain a replacement). Always carry blank paper logs in your truck for this purpose.
Inspector access
During a roadside inspection or safety audit, you must be able to display the previous 7 days of records to the inspector either on the device's screen or via printout, email, or web service. Failure to produce records on demand is itself a violation regardless of underlying HOS compliance.