It's different to the three bridges route.
If its the same one I've done and I'm pretty sure it is you start at the same spot 'salt ayre running track then 3/4 of the adjacent cycle circuit and then out briefly onto the main road and down to the rail bridge [Carlisle bridge] and come back to the cycle track and follow the river Lune up to 'Snatchems - Golden Ball pub area'.
You take a right at the end of the path and run towards the new bye pass road and actually run along the bye pass towards Heysham, then at the first round a bout take a left sign post Overton / Middleton and then soon after left again along the 'liable to flood at high tide road' past the Golden ball pub this time [stop for a quick pint] and down the cycle path again on to the cycle circuit briefly and one lap of the running track to finish. !
Lovely and flat and a nice area to run.