G. Changeable message board signs existing in accordance with the requirements of former subsection 11 continue to exist if the signs:

(1) Are reasonably incapable of being modified or reprogrammed to comply with this section as amended; and

(2) Are not replaced, substantially rebuilt, reconstructed or repaired beyond routine maintenance.

H. The size, intensity of illumination and acceptable rate of change between the time display and the temperature display of a time and temperature sign must comply with rules, policies or guidelines adopted by the Department of Transportation. Rules adopted pursuant to this section are routine technical rules as defined in Title 5, chapter 375, subchapter II-A 2-A. Time and temperature signs erected prior to September 29, 1995 need not comply with those rules, policies or guidelines.