The Transportation Safety Board says the placement of the horn on a locomotive contributed to a deadly collision between a Canadian National freight train and a road grader in Saskatchewan.

The board says the engine horn sounded several times before the January 2013 crash near Paynton, northwest of North Battleford.

But it says the horn wasn't as loud as possible because it was placed in the middle of the locomotive in a recessed location and -- combined with the noise inside the grader cab -- the driver had less than two seconds of audible warning.

The board also says the grader driver's attention was likely focused on resetting the blades for snow clearing at the crossing and he didn't detect the approaching train.

The driver of the grader was killed.

The locomotive and 16 tank cars carrying petroleum crude oil derailed and about 106,000 litres of oil spilled from four cars.