AN AIR CARRIER PILOT DESCRIBES HIS CONFUSION AT SEEING TAXIWAY LIGHTS ON DTW RUNWAYS 4R/22L AND 4L/22.

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THERE IS A VERY UNORTHODOX TXWY LIGHTING SYSTEM ARRANGEMENT AT DTW. THERE IS NO DISTINCT SEPARATION WITH THE TXWY LIGHTING SYSTEM FROM WHERE THE RWY MEETS THE TXWY AND THE OPPOSITE IS TRUE. AT SEVERAL LOCATIONS; BLUE TXWY LIGHTS ARE INTERTWINED WITH WHITE RWY LIGHTS. BECAUSE THE RWY LIGHTS ARE DIRECTIONAL AND CANNOT BE VIEWED AT THE 90 DEG ANGLE; AT CERTAIN INTXNS THE RWY CAN BE EASILY MISTAKEN AS TXWYS. DTW PLACEMENT OF BLUE TXWY LIGHTS DIRECTLY ON THE RWY ENVIRONMENT IS A SERIOUS POTENTIAL HAZARD AND NEEDS TO BE INVESTIGATED ASAP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER NOTED THAT WHEN HE EXITED RUNWAY 22R AT TAXIWAY A4 HE NOTED BLUE TAXIWAY LIGHTS ON THE RUNWAY'S EDGE AND THOUGHT AT THE TIME IT WAS ODD. SOMETIME LATER ON TAXIWAY Y SOUTHBOUND HE NOTED BLUE TAXI LIGHTS AT A8 MIXING WITH RUNWAY 4R EDGE LIGHTS AND THEN EXITING AGAIN AT Y9. THE REPORTER FOUND THAT PLACING BLUE TAXIWAY LIGHT IN THE RUNWAY ENVIRONMENT CAUSED CONFUSION AND THAT IN A VERY LOW VISIBILITY TAXI ENVIRONMENT THIS CONFIGURATION MAY HAVE UNINTENDED CONSEQUENCES. THE REPORTER BELIEVES A PILOT HAVING LANDED ON A RUNWAY AND THEN ENCOUNTERING TAXIWAY LIGHTS WITHOUT BEING ABLE TO SEE THE ENTIRE ENVIRONMENT COULD COME TO EXPECT THAT A TRANSITION TO A TAXIWAY HAD OCCURRED WHEN IN FACT THE AIRCRAFT WAS STILL ON THE RUNWAY. THE ADDITIONAL EXPERIENCE THE PILOT DESCRIBED WAS THE EFFECT OF SEEING A RUNWAY AS A TAXIWAY. THIS COULD OCCUR BECAUSE THE RUNWAY LIGHTS CANNOT BE SEEN BEYOND 90 DEGS AND A RUNWAY WILL APPEAR AS A TAXIWAY WHEN THE TAXIWAY LIGHTS CAN BE SEEN BUT NOT THE RUNWAY LIGHTS AS WHEN AN AIRCRAFT IS TAXIING IN THE OPPOSITE DIRECTION FROM THE ACTIVE RUNWAY.