An electronic logging device (ELD) connects to a truck's engine and records the driver's hours of service on its own. This guide covers what an ELD records, who must use one, the exemptions that matter for construction fleets, and what happens when a device fails.
An ELD (electronic logging device) in trucking is a small device that connects to the truck's engine and records the driver's hours of service (HOS) on its own. The FMCSA has required ELDs since December 18, 2017, for most drivers who must keep records of duty status (RODS).
The device reads time, location, engine hours and miles straight from the truck. The log shows what the truck did, not what someone wrote down later. Construction fleets meet the rule through their on-road trucks. Clue pulls GPS and telematics data from those same trucks into one record per machine, next to inspections and repairs.
Key Takeaways
An ELD records the date, the time, the truck's location, engine hours, vehicle miles, and the identity of the driver, the vehicle and the carrier. It writes these at engine start and shutdown, at every duty-status change, and once an hour while the truck is moving.
| Data point | When the ELD writes it | What it settles |
|---|---|---|
| Date, time and location | Each duty-status change, and hourly while driving | Where the truck was when the clock moved |
| Engine hours and vehicle miles | Engine start, engine shutdown and each recording | What the truck did between entries |
| Duty status | When the driver changes it. Driving sets itself once the truck moves | The record an inspector reads first |
| Driver and co-driver identity | At login | Whose hours the time counts against |
| Vehicle and carrier identity | With every record | Which truck and which company the log belongs to |
| Malfunction events | When the device finds a fault | Starts the 8-day repair clock |
Drivers keep some privacy. During approved personal use, the location stamp is blurred to about a 10-mile radius. Edits are allowed with a note, the original entry stays in the file, and driving time the device recorded on its own can never be shortened.
An ELD plugs into the truck's engine control unit, usually through the diagnostic port. It takes engine power, motion, miles and hours from the engine itself. The driver sees the log on a screen in the cab and picks a duty status: off duty, sleeper berth, driving or on duty.
Driving records itself. Once the truck is in motion, at a threshold no higher than 5 miles per hour, the device switches the driver to driving. Miles driven with no one logged in become unassigned driving time. The carrier must assign that time to a driver or explain it.
At a roadside inspection, the driver sends the log by web services or email, or hands it over by USB or Bluetooth. The screen or a printout works as backup. Only devices registered with the FMCSA satisfy the rule, and the maker self-certifies each model to get on that list.
A motor carrier operating commercial motor vehicles must install and require each of its drivers to use an ELD to record the driver's duty status ... no later than December 18, 2017. — 49 CFR § 395.8(a)(1)(i)
The ELD mandate covers drivers who already must keep RODS while operating a commercial motor vehicle (CMV). It added no new names to the logging rules. It changed the medium. Paper gave way to a registered device, and the older recorders (AOBRDs) aged out at the end of 2019.
| Exception | Who it covers | What it means |
|---|---|---|
| Short-haul | Drivers who stay within a 150 air-mile radius and are released within 14 hours | No RODS at all. Time records instead, so no ELD |
| 8 days in 30 | Drivers who need RODS on no more than 8 days in any 30-day period | Paper logs are fine on those days |
| Driveaway-towaway | The vehicle being driven is the shipment | No ELD in the delivered vehicle |
| Pre-2000 | Vehicles made before model year 2000, by the VIN on the registration | Exempt from the device, not from the hours rules |
The full list sits in 49 CFR 395.1(e). Most construction trucks live inside the short-haul exception. The driver leaves the yard, runs local sites, and is released the same day. Short-haul skips the logbook, not the walkaround. The daily DVIR still applies. The trap is the ninth day. Break the short-haul limits on more than 8 days in a 30-day window and the truck needs an ELD.
ELD logs, eLogs and electronic RODS all name the same record: the duty-status log the device produces. An inspector reads that record against the HOS limits. For property carriers that means 11 hours of driving inside a 14-hour window, a 30-minute break after 8 hours of driving, and a 60- or 70-hour weekly cap.
DOT officers pull these logs at roadside checks and during audits. A clean log file is the fastest way through both. The FMCSA wrote in the final rule that the requirements for ELDs “will improve compliance with the HOS rules.” That is the whole idea. The device makes the record honest.
One box in the cab often does three jobs. Only one of the three is required by law. Buyers mix them up, which is how a fleet ends up compliant yet still blind to what its trucks are doing.
| System | Main job | Required by law? |
|---|---|---|
| ELD | Record hours of service | Yes, for drivers who keep RODS |
| GPS tracking | Show where the truck is now | No |
| Telematics | Stream engine data, fault codes and use | No |
The mandate covers the hours part. The other two feeds are where a fleet earns its money back. Clue reads GPS and telematics data from the providers a fleet already runs, so dispatch sees every truck on one map in Clue's fleet tracking, and the shop sees fault codes next to each truck's service history in Clue's maintenance software.
Take a tandem dump truck that works within 40 miles of the yard. The driver clocks in, runs local hauls, and is released nine hours later. Short-haul covers all of it. No RODS, no ELD, just time records.
Then the company wins a job 170 air miles out. The same driver hauls material there nine days in one month. Days one through eight can run on paper logs. Day nine breaks the 8-days-in-30 allowance, and from that day the driver must log on a registered ELD. A fleet that tracks haul distances sees the ninth day coming before it arrives.
These are the ELD questions that come up most when a fleet first meets the mandate. Each answer stands alone, so you can drop one into a driver briefing without rewriting it.
A GPS tracker reports where the truck is. An ELD records the driver's hours of service, and it uses GPS to stamp location onto that log. Only a registered ELD satisfies the FMCSA logging rule. Many fleets run one device that does both jobs.
Date, time, location, engine hours, vehicle miles, and the identity of the driver, the vehicle and the motor carrier. The device writes these at engine start and shutdown, at each duty-status change, and once an hour while the truck is moving.
Only when their drivers must keep records of duty status. Many construction trucks run under the 150 air-mile short-haul exception and never need one. Off-road machines never do. An excavator is not a commercial motor vehicle, whatever its size.
The driver notes the fault, tells the carrier within 24 hours, and rebuilds the current day plus the last 7 days on paper if the device lost them. Paper logs continue until the unit is fixed. The carrier has 8 days to repair or replace it.
Yes, with limits. A driver or the carrier can correct an entry. Every edit carries a note, and the original stays in the file. Driving time the device recorded on its own can never be shortened, by anyone.
Many newer trucks ship with factory telematics that can run ELD functions through the maker's own system. The function still has to be registered with the FMCSA to count. A built-in system that is not on the registered list does not satisfy the rule.
