Mono: Motion Relating to the Built Environment

Here's my MM challenge blip today, for ApolloFly's hosting of the MonoMonday challenge. I popped along to our local Metro station and played with the Neutral Density Long Exposure mode on the camera. I got a few different effects but this is the one I liked best. It looks best large.

(Most of our Metro rolling stock is 40+ years old and tends to fail frequently. We've been promised new stock on and off for years: recently it's started to arrive from the manufacturers in Switzerland and we've chanced to get a ride on one or two recently. They're certainly quieter and smoother than the old ones - but all 5 in use so far have just had to be taken out of service while they sort out a problem with the doors. There seems to be a dispute between the manufacturers and the drivers as to whether it's driver error or a software fault - I understand that sometimes the doors have been opening on the wrong side! Hopefully it can be sorted out quickly.)