Im guessing you havent tried getting from Chester le Street towards Whitemare Pool during the morning rush hour?
There are tailbacks at Washington Services and traffic can get back beyond the Follingsby junction on the A194. It would potentially be as quick going to the P&R at Heworth on some mornings.

We all know the line will never go into central Washington. The only way it could, would be for an extention to be built from the Leamside Line towards the Galleries and have a load of housing demolished at the same time.