Colin McKenzie écrivait
:

There is no driver on board of the line 14 trains in Paris. On the
other hand, there is a hidden dashboard in the front car permitting
an agent to manually drive the train in the event of an emergency.

How does he get there if the train is stuck in a tunnel?

He can walk in the tunnel (they are enough wide that people could walk
beside a train).

Are RATP tunnels single or double track?

They are generally double tracked, but some section of the line 14 are
single tracked.