Through the Mersey tunnel in Liverpool, Is there a pedestrian access?

NO, but with rare exceptions.

-- emergencies, and i recall once in a blue moon.

There is a walk way through it but as the first answerer says, it's for emergencies. It's also for the maintenance workers use.

The Mersey Tunnel is a Railway tunnel. No pedestrian access through this nor the Queensway or Kingsway.

The Mersey Tunnels connect Liverpool with the Wirral Peninsula, under the River Mersey.

There are three tunnels: the Mersey Railway Tunnel (opened 1886), and two road tunnels, the Queensway Tunnel (opened 1934) and the Kingsway Tunnel (opened 1971). The railway tunnel and Queensway Tunnel connect Liverpool with Birkenhead, while the Kingsway Tunnel runs to Wallasey.

The road tunnels are owned and operated by Merseytravel, and have their own police force, the Mersey Tunnels Police.

No. But there is emergency only exit routes

No. The only ways over are the Mersey Ferry from Princes Dock, the bus, or Wirral Line on the Metro.

Every now and again, they have a charity walk through it.

Whilst generally there is no pedestrian access to either tunnel, on some Sundays open days are advertised when the public can walk through the Queensway (1934) Tunnel in organised tours and see behind the scenes. Obviously it is closed to traffic on these open days.

On occasion this tunnel is also closed to traffic to allow marathon runs and cycle races to use it.

Interestingly, a rather fanciful illustration published before the completion of the Queensway Tunnel showed pedestrians on pavements at the side. the nearside lane being used by horse-drawn traffic and the offiside lanes by motor traffic.

No. If there was you'd have to be a little soft in the head to use it. I find both of them bad enough to drive through