Conduct Yearly Solar Panel Maintenance Including Surface Cleaning and Charging Output Tests When Using Solar Powered Intelligent Warning Devices

Minnesota Department of Transportation’s Reference Guide on How to Deploy Intelligent Warning Devices.

Date Posted

Guidelines for Using Intelligent Warning Devices

Summary Information

Intelligent Warning Devices (IWD) are advanced traffic control and safety devices equipped with intelligent features to enhance the effectiveness of warnings and improve overall road safety. The objective of this study was to provide local traffic agencies a reference guide on four IWD in terms of a general explanation on the use of the signs and their effectiveness, recommended installation protocols, maintenance considerations, and alternative countermeasures to consider. The four IWD covered in this reference guide were (i) Light Emitting Diode (LED) Enabled Signs which include embedded LEDs within a sign's symbol, legend or border to improve its conspicuity, (ii) Radar Speed Feedback Signs, which were speed measuring devices, which consisted of loop detectors or radars, and a message sign that displayed feedback to drivers that exceed a predetermined speed threshold, (iii) Rectangular Rapid Flashing Beacons, which were rectangular shaped high intensity LED signs with yellow flashing lights activated by a pedestrian push button, and (iv) Dynamic “No Turn on Red” Signs that illuminated when right turn movements on red were not allowed at a signalized intersection.

  • Conduct yearly solar panel reviews including surface cleaning and charging output tests when using any solar powered systems. While these systems often use maintenance-free batteries, it is recommended to annually test battery output to ensure compliance with the manufacturer's specifications. Agencies should also prepare for solar panel replacements at the end of their effective lifespan, typically between 25 to 30 years. 
  • Plan for harsh weather conditions where applicable. In locations with cold winter climates, challenges may arise when using solar power without a hard-wired backup. Therefore, careful consideration must be given to when it is appropriate to use solar power versus hard wiring alone or with backup to ensure uninterrupted operations.
  • Use good engineering judgement to avoid redundancy when placing IWD. Signs should be used when warranted and not implemented everywhere. Detailed review of existing studies on how these devices influence user compliance should be conducted before considering a specific IWD implementation. As mentioned in this study, LED enabled signs, for example, could be warranted if a certain location has a history of crashes documented to be caused by a failure to stop or adherence to warning, or if there are low visibility issues. 
  • Ensure all signs are within the lines of sight of the drivers. It is important to make sure that signs are appropriately placed not only to ensure visibility for drivers, but also to prevent any overlap or obstruction between them. 
  • Consider potential impacts of the IWD prior to installation. It is important to seek stakeholder feedback and carefully evaluate any residential impacts of the signs in advance before actual sign placements. 
  • Exhaust other countermeasures first before deciding on installing any IWD. It is good practice to use engineering judgment to evaluate the conditions and determine whether a certain alternative safety enhancement is more appropriate to increase pedestrian safety, less costly, or easier to implement than IWD.
System Engineering Elements

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