"This document provides design guidelines@ test procedure references@ and performance requirements for directional@ single color@ flashing optical warning devices used on authorized emergency@ maintenance and service vehicles. It is intended to apply to@ but not limited to@ surface land vehicles. Rationale 1. Multiple flash patterns and cyclic patterns have been added. End users have increasingly been requesting non-repetitive flash patterns to prevent complacency. 2. Source definition has been changed to include multiple source components with some restrictions. Light pulse and flash definitions have been added. 3. The specified minimum size lighted area has been eliminated. Recent demonstrations have shown that observers were unable to see any difference in the performance of flashing warning devices having the same optical power but substantially different lighted area. 4. Optical Power has been defined. 5. Class 1@ 2 and 3 ratings have been established. Lighting identification code restrictions have been added. Multiple flash patterns that are user adjustable must be rated as the lowest performance mode. 6. Test Voltage - In conformance with other optical warning device reports@ the test voltage is changed to 12.8 V for 12 volt systems and 25.6 V for 24 volt systems instead of ""the voltage recommended by the manufacturer""@ and requirements added for 36 volt systems. 7. Environmental tests have been added - these include low temperature@ high temperature and 200 hour durability flash rate maintenances. 8. Photometric performance has now been established as meeting the original peak intensity and meeting a specified ""optical power"". Advances in laboratory instrumentation have made it practical and cost effective to directly measure the optical power generated by any optical warning device. The direct measurement or calculation of peak intensity also is readily done with current technology. 9. Establishment of new performance requirements for use of the color blue. The use of blue as a signal color for emergency vehicles has steadily increased until now approximately one half of such vehicles employ blue either alone or in combination with red or white. It is apparent that the operators of emergency vehicles have determined that the spectacular performance of blue at night outweighs the very poor performance of this color during the day. Blue requirements shall be the same as red. 10. Eliminated the requirement that the device or system use a J945 or J1054 compliant flasher. Devices not supplied with flasher shall be tested using a 1.20 Hz / 50% duty cycle flasher. 11. The flash rate range was increased from 1-2 Hz to 1-4 Hz. Increasing the flash rate without a corresponding increase in photometric energy lowers the flash energy. However@ if the flash rate is increased and the photometric energy is maintained above the minimum requirement@ the conspicuity of the signal is improved. From a practical stand point@ higher flash rates reduce the travel distance between signal flashes and promote earlier recognition of a hazardous condition. This document increases the allowable flash rate maximum to 4 Hz@ so long as the flash energy content of the signal is not reduced below the required tabulated values. It is important to note that the energy to operate such devices may have to increase with the flash rate. This also harmonizes with ECE Regulation 65. 12. Miscellaneous Editorial Changes - The word ""device"" is used to indicate the assembly of components which is tested. The previous edition used both the words ""lamp"" and ""device"" for this purpose as well as referring to light sources as ""lamps."" 13. The color green was discussed and deemed not applicable."