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The purpose of the following research was to determine whether conspicuity of an illuminated traffic signal lens could be increased with a modulating incandescent light source. Experiments were conducted both in the laboratory and a controlled field setting under normal and degraded viewing conditions using both static and dynamic testing situations. Four experiments are reported here. There were four other experiments conducted which are not reported here. Some of these served as the basis for later studies. Briefly, the first study required drivers to perform a distractor task of operating a simulated vehicle generated on a monitor by a microcomputer in the presence of simulated sun backlighting on a traffic signal face. The second required subjects to identify their driving response (e.g., stop and wait, stop and go) when confronted with the standard non-modulating light, two patterns of a blinking light (one and two/sec), and a modulating light of 4/sec. The third study examined a driver’s identification of range of modulation while wearing special glasses simulating early/moderate stages of cataract development. The fourth study examined the modulating bulb in a traffic signal face under degraded conditions of simulated fog produced by special “fog” glasses. These latter two studies were conducted at the automotive test track at the Pennsylvania Transportation Institute, Pennsylvania State University.

The results of the studies reported here showed that under a degraded viewing conditions of sun backlighting the modulating bulb was more effective in increasing the conspicuity of the illuminated lens than the standard bulb now in use. The next step in the research process is to test the modulating bulb at an actual intersection. Plans are underway to conduct such a study in the City of Oneonta.

Concern was raised as to whether the modulating light source may initiate photos nsitive induced epileptic seizures. Previous research was examined and neurological expert evaluations were sought to explore this possibility. Briefly, the literature and experts' opinions indicated that the unique lighting pattern would not trigger a photosensitive induced epileptic seizure. Attached is a report submitted to the FHWA concerning photosensitive induced seizures.