Turns

A3D_GetRouteTurn and A3D_GetRouteProgress give the turns of a route as an A3D_TURN, by the angle between the road before the junction and the road after it.

Turn	Value	Angle
A3D_TURN_NONE	0	No turn is left, the end comes next
A3D_TURN_SLIGHT_LEFT	1	25 to 60 degrees to the left
A3D_TURN_LEFT	2	60 to 120 degrees to the left
A3D_TURN_SHARP_LEFT	3	120 to 160 degrees to the left
A3D_TURN_SLIGHT_RIGHT	4	25 to 60 degrees to the right
A3D_TURN_RIGHT	5	60 to 120 degrees to the right
A3D_TURN_SHARP_RIGHT	6	120 to 160 degrees to the right
A3D_TURN_BACK	7	More than 160 degrees, or turning around

Which turns count

• Only junctions where more than two ways meet give turns, besides turning back. A road that bends between junctions, however sharply, gives none.
• A change of less than 25 degrees is going on, and gives no turn.
• Turns less than 25 metres apart count as one, with their angles added. Crossing a divided road to turn left is one left turn, not a left turn and a right turn.
• A route that starts against the heading of A3D_FindRoute begins with A3D_TURN_BACK at its first point.

What they cost

The routes for vehicles pay for each turn as they search: two seconds to the right, five to the left and thirty to turn back. A turn to the right is cheaper because it crosses no lane of the traffic coming the other way. Going on costs nothing, and a turn of less than 30 degrees counts as going on. See Route types.