OVER 400 OVERTAKING MANOEUVRES WERE OBSERVED ON A TWO LANE BRITISH "A" CARRIAGEWAY WITH A MAXIMUM SPEED LIMIT OF 100 KM/HR. IT WAS FOUND THAT 14 PER CENT OF OVERTAKING DRIVERS USE A GAP SIZE TOO SMALL (I.E.LESS THAN 400 M) TO COMFORTABLY ACCOMODATE VEHICLES CLOSING ON EACH OTHER AT NORMALLY ASSUMED DRIVING SPEEDS. ACCEPTANCE OF A SMALL GAP FOR OVERTAKING INCREASED THE INCIDENCE OF LANE SHARING (OVERTAKING PARTIALLY IN BOTH LANES) AND CUTTING IN (PRECIPITOUS RETURN TO THE DRIVING LANE). WHEN ONLY A SMALL GAP WAS AVAILABLE, THERE WAS AN INCREASE IN BOTH LANE SHARING AND CUTTING IN, USUALLY ONLY ONE OF THE ABOVE OPTIONS WAS UTILISED WITH A TENDENCY FOR PIGGY-BACKERS (TWO OR MORE SIMULTANEOUS OVERTAKERS) TO PREFER LANE SHARING WHILE NON-PIGGY-BACKERS PREFERRED TO CUT IN. FLYING OVERTAKERS (OVERTAKING WITHOUT PAUSE), ACCELERATIVE OVERTAKERS (OVERTAKING AFTER A PAUSE), PIGGY-BACKERS, NON PIGGY-BACKERS AND DRIVERS NOT BRAKING TO FOLLOW BEFORE OVERTAKING, ALL CUT IN MORE IN SMALL GAPS THAN IN LARGE GAPS. ONLY DRIVERS BRAKING TO FOLLOW FAILED TO CUT-IN MORE IN SMALL GAPS. IN ADDITION, ACCELERATIVE OVERTAKERS, PIGGY-BACKERS, NON PIGGY-BACKERS, DRIVERS BRAKING AND DRIVERS NOT BRAKING TO FOLLOW, LANE SHARED MORE IN SMALL GAPS THAN LARGE GAPS. ONLY FLYING OVERTAKERS FAILED TO LANE SHARE MORE IN SMALL GAPS THAN IN LARGE GAPS, BUT THIS WAS BECAUSE THEY DID A LOT OF LANE SHARING IN BOTH LARGE AND SMALL GAPS. FINALLY, FLYING OVERTAKERS, PIGGY-BACKERS AND DRIVERS WHO BRAKED IN ORDER TO FOLLOW BEFORE OVERTAKING, WERE MORE LIKELY TO ACCEPT A SMALL GAP FOR OVERTAKING THAN WERE ACCELERATIVE OVERTAKERS, NON PIGGY-BACKERS AND DRIVERS WHO DID NOT BRAKE TO FOLLOW. POLICY AND RESEARCH IMPLICATIONS OF THESE FINDINGS ARE DISCUSSED. (Author/publisher).
Abstract