What’s a GPS WN Rollover Event?

And How to Avoid an Outage

Electronic logging devices have a long-established track record for reliability and accuracy. Fleets have used them since before a federal mandate was even in the works.

But they’re not foolproof. Some manufacturers in the past have experienced a GPS week number (WN) rollover event – which can cause telematics units to miscalculate time and a receivers location.

A rollover event occurs when the Coordinated Universal Time (UTC) clock used by the satellite navigation system reaches its 10-bit limit for counting the number of weeks since the beginning of the current GPS “epoch”: August 21, 1999.

After 1,024 weeks, a clock reaches the limit for its 10-bit “week number” (WN) counter and flips back to 0000000000. In some cases, a firmware update to get units working again may be required. This means drivers would have to use paper logs until this is completed.

Most newer GPS receivers, including Transflo’s T-Series ELDs, are programmed to accommodate a 13-bit WN counter. These types of devices will NOT experience a rollover event for approximately 150 years.

A WN rollover event illustrates the importance of “good ol’ paper backups” and reminds drivers what to do in the event of an ELD malfunction:

  • Contact your carrier in writing within 24 hours.
  • Reconstruct your record of duty status for the current 24-hour period and the previous 7 consecutive days. Do this by using graph-grid paper logs or electronic logging software (unless you already have records or retrieved them from the ELD).
  • Use paper logs or another compliant method until your ELD is back in service.

Rollover events highlight the need for customer support and, when necessary, updates to firmware that makes an ELD unit function.

Transflo partners with Geotab, the top-rated ELD device in the world, to bring you Transflo T-Series ELDs as part of Transflo Bundle+ (an ecosystem of solutions for the freight industry). With Transflo, fleet managers can collect data on each load, track truck/trailer locations, streamline operational expenses, and so much more.

And drivers get access to a single mobile app, Transflo Mobile+, which streamlines their whole work-day. This includes weigh station bypasses, truck-friendly navigation with GPS, dispatch chat, and their electronic logbook. All of this is accessible from one app on their mobile device.

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