Some terminology

Through this article I will use the abbreviation VMS in place of Variable Message Sign. This term refers to electronic road signs with programmable messages, wich are the main topic of this article.

The costs

The technology required to deploy and operate a traffic VMS is not cheap. These are some of the costs involved:

  1. Fuel required to transport the VMS to its destination. It usually weights around 1,500 pounds (682 kg)
  2. Rechargeable batteries or solar panels to keep it operating 24 hours a day. Prices for a single battery or solar panel are between $300 and $500 and these systems usually required two or three units.
  3. On board computer to create, edit and schedule the messages that will be displayed. This devices can cost between $400 and $700 dependig on capabilities
  4. Monthly cellular fee for a data plan if the VMS can be programmed remotely.

The problems

These are some of the problems that a VMS owner has to address:

  1. Stealing - As explained in the previous section, the components of a VMS are expensive. In the case of the batteries, even if they are old, they can be sold to recycling companies for a fraction of their original value. Thieves could earn $7.00 from a stolen $350 battery. There are thieves that even steal the whole trailer!
  2. Battery or solar panel failure - batteries can fail over time or discharge faster. It is important, sometimes critical, to maintain a VMS operating uninterrupted and preventive measures must be taken.
  3. Communications failure - messages are managed through the onboard computer. Updating messages remotely would be impossible if communications fail because of network or hardware problems.

How GPS devices can help

Enhanced GPS tracing devices can help adressed each of the issues raised in the last section:

  1. Stealing - hardware with similar functionalities as an Automatic Vehicle Location device can report its location at a constant interval, for example every 15 minutes. If the equipment has a motion sensor it can be programmed to immediately report on vibration or battery voltage drop, that way it gives the owner an opportunity to react and verify if there is a robbery in progress.
  2. Battery failure or solar panel - this problem can be prevented or promptly resolved if voltage readings are sent through a GPS enabled device with a voltage sensor attached to the battery. Most tracking equipment provide extra input ports for sensors and other add-ons.
  3. Communications failure - software can be obtained or developed that tries to reach the onboard computer every few minutes and sends an alarm to the owner by email or SMS when communications are not possible.


The Return On Investment (ROI) of implementing a GPS tracking solution for electronic road signs will be driven by:

  • only when necessary battery or solar panel replacements, implying less hours of labor and better use of units life
  • theft prevention and recovery
  • and last, but not least, customer satisfaction as a result of a reliable system