Quick Answer
An ELD (Electronic Logging Device) is hardware that connects to a commercial truck's engine and automatically records the driver's hours of service — driving time, engine hours, miles, and duty status. The FMCSA requires most commercial motor vehicle drivers to use a registered ELD instead of paper logs to prove compliance with federal Hours of Service rules.
Key Takeaways
- An ELD plugs into the vehicle's diagnostic (OBD) port and records driving time automatically from engine data.
- It replaced paper logbooks under the FMCSA ELD mandate, fully in effect since December 2019.
- Only ELDs listed on the FMCSA's registered-device list are legal — checking the list is the carrier's responsibility.
- Most interstate CMV drivers need one, but several exemptions exist (pre-2000 engines, short-haul, and more).
What does ELD stand for?
ELD stands for Electronic Logging Device. It's an electronic tool that automatically records a driver's driving time and other Hours of Service (HOS) data, making record-keeping more accurate than the old paper logbook system.
How does an ELD work?
An ELD connects directly to the engine control module through the vehicle's diagnostic port. From there it captures whether the engine is running, whether the vehicle is moving, how many miles are driven, and total engine hours. That engine data is paired with the driver's own duty-status selections — off duty, sleeper berth, driving, or on-duty — inside a mobile app.
The result is a tamper-resistant record of duty status (RODS) that syncs to fleet software in real time and can be handed to an inspector at the roadside in seconds. Because the driving segments come straight from the engine, drivers can't simply "forget" to log time the way paper logs allowed.
What data does an ELD record?
- Driving time and duty status (D, ON, OFF, SB)
- Engine hours and vehicle miles
- Date, time, and location at each status change
- Vehicle and driver identification
- Malfunction and data-diagnostic events
Who has to use an ELD?
Most drivers of commercial motor vehicles who are required to keep records of duty status must use a registered ELD. This covers the majority of interstate trucks and buses. There are exemptions — short-haul drivers within a 150 air-mile radius, vehicles with engines older than model year 2000, driveaway-towaway operations, and drivers who keep paper logs no more than 8 days in any 30-day period. See our full guide to ELD exemptions.
Is any ELD legal, or does it have to be registered?
It must be registered. Manufacturers self-certify their devices against the FMCSA's technical standards and register them on the agency's official list. The FMCSA also revokes devices that fall out of compliance. If you're running a revoked device, you can be cited and placed out of service — so the carrier is responsible for periodically checking both the registered and revoked lists.
What's the difference between an ELD and an AOBRD?
AOBRDs (Automatic On-Board Recording Devices) were the older technology allowed before the mandate. They had looser requirements and were phased out — since December 16, 2019, only true ELDs satisfy the rule. If someone offers you an "AOBRD," it's no longer compliant.
This post is educational and not legal advice. Confirm your obligations with the current FMCSA regulations.
FAQ
Do owner-operators need an ELD?
Yes — if you drive a commercial motor vehicle interstate and are required to keep RODS, the mandate applies to you whether you run one truck or a hundred, unless you qualify for a specific exemption.
Does an ELD track my location all the time?
An ELD records location at each duty-status change and at set intervals while driving — not continuous real-time surveillance of off-duty movement. Location is recorded at lower precision during personal conveyance.
Can I still use paper logs?
Only if you fall under an exemption (such as the 8-day rule) or during a temporary ELD malfunction, when you may use paper logs for a limited period while the device is repaired.
