I'm not sure that the traffic count restriction has made TTing safer, but it has certainly made it fairer. Back in the day, some of the fast people wouldn't bother to start on the A34 if they were on the first half of the start sheet, because the late starters got so much of a tow from the heavier traffic that you pretty much couldn't win a prize off a start number lower than 60.
I'm not sure that the traffic count restriction has made TTing safer, but it has certainly made it fairer. Back in the day, some of the fast people wouldn't bother to start on the A34 if they were on the first half of the start sheet, because the late starters got so much of a tow from the heavier traffic that you pretty much couldn't win a prize off a start number lower than 60.