Narrative:

Started engine and requested taxi. Cleared to taxi to runway 5R. Looked ahead and saw ramp extending straight ahead and what I interpreted to be additional ramp to the left and parallel to ramp extending ahead of us. So I taxied onto the hard surface to the left as it was more clear of possible obstructions than going straight ahead. As I taxied, I noted a lack of yellow lines and was shocked to realize I was on runway 5L. I asked ground if it was ok to go that way and was told 'that's fine.' I was appalled -- really appalled -- at how easy it was to enter the runway. It was not in use at the time, thankfully. I have always taken runway incursion reports seriously -- consciously stating aloud as I was about to enter any runway for any reason for concurrence from the first officer. In trying to figure how it could have happened, I believe I misinterped runway 5L as a taxiway because it was parallel to and right next to the ramp. In the future, I refuse to taxi anywhere without a yellow line unless I completely understand exactly what the surface is and vocalize that understanding to the first officer. I am still shocked how easy it was to make such a mistake. You cannot be too careful about surface movement -- even when you think you are.

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Original NASA ASRS Text

Title: MD SUPER 80 CAPT INADVERTENTLY TAXIED ONTO ACTIVE RWY DURING TAXI OUT DUE TO MISINTERPING THE RWY FOR A PARALLEL RWY.

Narrative: STARTED ENG AND REQUESTED TAXI. CLRED TO TAXI TO RWY 5R. LOOKED AHEAD AND SAW RAMP EXTENDING STRAIGHT AHEAD AND WHAT I INTERPED TO BE ADDITIONAL RAMP TO THE L AND PARALLEL TO RAMP EXTENDING AHEAD OF US. SO I TAXIED ONTO THE HARD SURFACE TO THE L AS IT WAS MORE CLR OF POSSIBLE OBSTRUCTIONS THAN GOING STRAIGHT AHEAD. AS I TAXIED, I NOTED A LACK OF YELLOW LINES AND WAS SHOCKED TO REALIZE I WAS ON RWY 5L. I ASKED GND IF IT WAS OK TO GO THAT WAY AND WAS TOLD 'THAT'S FINE.' I WAS APPALLED -- REALLY APPALLED -- AT HOW EASY IT WAS TO ENTER THE RWY. IT WAS NOT IN USE AT THE TIME, THANKFULLY. I HAVE ALWAYS TAKEN RWY INCURSION RPTS SERIOUSLY -- CONSCIOUSLY STATING ALOUD AS I WAS ABOUT TO ENTER ANY RWY FOR ANY REASON FOR CONCURRENCE FROM THE FO. IN TRYING TO FIGURE HOW IT COULD HAVE HAPPENED, I BELIEVE I MISINTERPED RWY 5L AS A TXWY BECAUSE IT WAS PARALLEL TO AND RIGHT NEXT TO THE RAMP. IN THE FUTURE, I REFUSE TO TAXI ANYWHERE WITHOUT A YELLOW LINE UNLESS I COMPLETELY UNDERSTAND EXACTLY WHAT THE SURFACE IS AND VOCALIZE THAT UNDERSTANDING TO THE FO. I AM STILL SHOCKED HOW EASY IT WAS TO MAKE SUCH A MISTAKE. YOU CANNOT BE TOO CAREFUL ABOUT SURFACE MOVEMENT -- EVEN WHEN YOU THINK YOU ARE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.