CMH CTLR DESCRIBED NEAR RWY INCURSION WHEN COORD WITH ARPT OPS REGARDING RWY OPENING WAS CONFUSED/ANTICIPATED.

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CHAIN OF EVENTS: RWY 28L/10R HAD BEEN CLOSED MOST OF OUR SHIFT FOR PAINTING. I WAS WORKING GND CTL. A CPR JET CALLED WITH A REQUEST TO TAXI FROM ONE FBO TO ANOTHER FBO. THESE FBO'S SIT DIRECTLY ACROSS RWY 28L/10R FROM EACH OTHER. THE MOST DIRECT TAXI RTE IS TO CROSS THE RWY AT C3/B3; WHICH IS JUST S OF OUR TWR. I COULD HAVE TAKEN THE JET TO CROSS AT TXWY F (WHERE WE WERE APPROVED TO CROSS THROUGHOUT THE CLOSURE); BUT I CALLED ARPT VEHICLE TO ASK IF I MAY CROSS AT C3/B3. ARPT VEHICLE SAID NO PROB; AS THEY WERE NEARLY DONE; AND WOULD BE GIVING THE RWY BACK TO US SHORTLY. ARPT VEHICLE SAID HE'D ADVISE LCL CTL WHEN THE RWY WAS OUR CTL. I CLRED THE CPR JET TO CROSS THE RWY AT C3/B3. SHORTLY THEREAFTER; I HEARD LCL CTLR ASKING THE PLT OF A C172 (ON A VERY SHORT FINAL TO RWY 28R) IF THEY WOULD LIKE TO SWITCH OVER AND LAND ON RWY 28L SINCE IT JUST OPENED. (THAT WOULD BE A MUCH SHORTER TAXI TO THEIR BASE). HEARING THAT; I IMMEDIATELY TOLD MY CPR JET TO HOLD SHORT OF THE RWY. THE C172 LANDED; AND TURNED OFF THE RWY WELL SHORT OF C3/B3. I 'THANKED' LCL CTL FOR CHKING WITH ME. WE HAVE A MAJOR VISIBILITY ISSUE FROM OUR NEW TWR. FOR INSTANCE; A SHORTER CTLR ON THE N SIDE OF THE CAB MUST TAKE SEVERAL STEPS TO THE S SIDE OF THE CAB TO BE ABLE TO SCAN THE ENTIRE LENGTH OF RWY 10R/28L. AND THEN THIS CTLR MUST TAKE SEVERAL STEPS BACK TO THE N SIDE OF THE CAB TO SCAN THE ENTIRE LENGTH OF RWY 10L/28R. (THE OTHER OPTION IS FOR THE CTLR TO STAND ON A 'RISER' THAT IS PROVIDED.) NOT ONE OF OUR CTLRS IS TALL ENOUGH TO SIMPLY TURN THEIR HEAD TO SCAN BOTH RWYS. ALL CTLRS MUST CONSTANTLY BE ON THEIR FEET; MOVING BACK AND FORTH; TO ADEQUATELY SCAN. OVER THE PAST 2 YRS THAT WE HAVE BEEN IN THIS NEW TWR; I HAVE OBSERVED THAT PROPER SCANNING OF THE RWYS HAS DETERIORATED. MOST OF THE TIME THE RISER SITS OFF TO THE SIDE; UNUSED; AND MANY CTLRS DO NOT MOVE ABOUT THE CAB TO SCAN BEFORE USING TKOF OR LNDG CLRNCS. TODAY'S NEAR RWY INCURSION WAS AN EXCELLENT EXAMPLE OF THIS DETERIORATION OF PROPER SCANNING.