I travel to work using the Jarrow end of this route through the Tyne Cycle / Pedestrian Tunnel.
It seems to be very popular in the summer when I see people on the C2C route.
The Howdon / Jarrow part isn't very cycle friendly even though the organisers will tell you differently.
There are supposed to be improvements soon alongside the new Tyne Tunnel building scheme, but they seem keener to put up weird modern sculptors, etc than to make the cycling safer.
The Cycle Tunnel itself is Class 2 protected, built in the 1950's and incorporates a wooden escalator system with 150 steps so they won't medernize it. We are stuck with it forever. It is not reliable and is often out of action for weeks or even months on end. The tiny lift (1M x 2M) was also out of action for a while last year and I had to carry my bike up the stairs - it nearly killed me. They say you can phone them for alternative transport but they send a flat bed truck which is not very good for the bike.
If you do the route it might be wise to check with them to see if the tunnel is fully accessible for cyclists to get through.
