The transportation industry is probably the biggest ELD user. And you’ll see why after we’ve defined what an ELD is.

What Is an Electronic Logging Device?

ELDs are hardware devices that record the driving time of commercial motor vehicles. They are plugged into vehicles’ onboard diagnostics (OBD) ports to record information about their engine, location, speed, distance driven, and more.

ELD usage has been a Federal Motor Carrier Safety Administration (FMCSA) requirement for most commercial vehicles since 2015. All companies that operate commercial vehicles (not just trucks) are mandated to use ELDs, including construction and passenger transit businesses.

How Does an ELD Work?

To make an ELD work, you begin by plugging it into a vehicle’s OBD port. By doing that, the ELD gathers data directly from the engine. It tells if the car’s engine is on or off, how much fuel it has used, and how far it has traveled. An ELD also has a built-in Global Positioning System (GPS) tracker to pinpoint a vehicle’s exact location.

The most effective ELDs give out real-time location information, allowing users to get the exact location of a vehicle at any time. Some have built-in gyroscopes and accelerometers that detect movements and give a vehicle’s driver visibility into safety-related events, such as harsh braking or turning.

Apart from collecting data, ELDs also transmit information to fleet managers in a company’s office. They can also give roadside inspectors data during inspections.

What Data Does an ELD Record?

An ELD records several kinds of information, including:

  • Drive time, hours of service (HOS), and duty status for ELD compliance
  • Real-time GPS location
  • Engine speed and load
  • Fuel efficiency, idling, and mileage
  • Diagnostics and fault codes
  • Safety-related events (e.g., harsh braking or collisions)

What Is an Electronic Logging Device For?

ELDs have multiple uses, which we’ll go into greater detail below.


ELDs compile so-called “e-logs” or records of a vehicle’s HOS and duty status. That eliminates manual logging into logbooks. The FMCSA’s ELD mandate requires most commercial vehicles to have an ELD for this purpose. That way, drivers can’t alter vehicle data or forget to document their work.

What Is the ELD Mandate?

Simply put, the ELD mandate keeps companies that operate commercial vehicles in check. While not all commercial vehicles are required to use ELDs and comply with the ELD rule, those used by drivers who must consistently track and maintain records of duty status (RODs) should.

Dispatch and Routing

The most advanced ELDs have a built-in GPS tracker that gives real-time location data that is useful for dispatch and routing. Companies can see where all their vehicles are anytime without calling their drivers.


ELDs that can be connected to OBD ports can pull critical engine data, such as mileage and fault codes. That information can help schedule a vehicle for preventive maintenance and repairs. Advanced ELDs also come with a smartphone app that drivers can use to complete electronic driver vehicle inspection reports (DVIRs). That allows them to reduce paperwork for offices.


ELDs with built-in gyroscopes and accelerometers can detect harsh braking and turning and collisions. This data can serve as a basis for designing driver training on safe driving. Historical location data can also help drivers avoid false accusations.

Security and Loss Prevention

The most effective ELDs have additional software to improve security and prevent loss. One with a geofencing feature lets owners create a virtual boundary around their terminal. Aided by the ELD’s real-time GPS capability, they can get alerted anytime a vehicle leaves the geofence, allowing them to avoid theft.


Most ELDs also have robust reporting features, helping companies identify problems and address these to save on costs. A fleet manager can, for instance, see idle times and extreme events. This information can help them create customized driver training, reduce fuel costs, and minimize risks related to driving behavior.

ELDs are a must for companies that want to comply with FMCSA and Department of Transportation (DOT) rules and regulations. They help not just fleet owners and drivers but also law enforcement agents. But ELDs differ from supplier to supplier. If you want the best ELD for your vehicles, choose one that ticks all the boxes in this comprehensive ELD guide.