There are additional traffic lights on the blackwall tunnel further in and a slip road out that can be used for overheight vehicles. I do remember having a 10-15 minute wait once while they sorted things out when a lorry driver got caught.
I'd have a feeling there are automated signs prior to the tunnel (or at least used to be) but I've not been through the tunnel for a year or so and things will have changed with the Silvertown tunnel opening.
I have seen someone not paying attention at the Rotherhithe tunnel and the roof of their van was a mess (and they're going to pick up a fine probably due to restrictions, the 2 tonnes gross weight limit is lower than a lot of van drivers expect)
As far as I'm aware they do need an act of parliment to close it down. The one to create the market on the current site is an Act of Parliament (The Metropolitan Meat and Poultry Market Act of 1860) which should protect the site from becoming anything but a place to provide Meat & Poultry
There is a detailed description of the circuit with the PAL colour card (it's on the euro //e motherboard) in Understanding the Apple //e by Sather (see archive.org for a copy) on pages 8-16 -> 8-19.
You do get the green/purple fringes on text, the euro //e has a switch on the motherboard that turns off the TCA650 and forces mono mode which is handy for 80 column work.
I _suspect_ you don't get all of the NTSC artifacts since PAL will be a bit better, but I really need to get my TV plugged in on my //e running one of the games (adventures typically) that use artifiacts to check.
The other alternative is the apple authorised ITT2020 which added an extra bit to the display so shows "jail bars" on screen when running ][ software. Again I should drag mine out to do some testing.
Interesting mention of Sidekick Plus, there was a complete SDK for it which I don't think ever got released anywhere (I had a copy as I was working for Borland at the time). It allowed multiple documents to be open at the same time.
It ran on top of several things. I remember the company I worked for (Alfa Systems) uploading IPX drivers to Novell for testing over a modem using IPX as a protocol.
Alfa designed Sage Mainlan originally a z8530 + RS485(?) PC card followed by a 10Mbps Ethernet with our own chip design (Enzo) fabbed as an ASIC by Toshiba. We wrote IPX drivers for both versions.
Interestingly we could hang systems with the 3COM cards in our test systems if we ran at full speed and at somepoint we had the full 500 metres of thick ethernet in the office.
The IPX version that came with Netware 3 was rather nice, I seem to recall it had a buffer of segments and these got filled by the different layers of the network stack as needed along with some fancy protocol filtering so your code only saw just the data packets it was interested in.
https://www.bbc.co.uk/news/articles/cx2qz89nk11o