That's definitely a general requirement for most hire boats on the inland waterways but IMX it isn't usually a restriction for anyone owning their own boat, and certainly wouldn't be for any remaining commercial traffic.
What does IMX mean please?
Very little if any commerical traffic these days.
Also where is any boats commerical or pleasure going in the dark after Selby Toll Bridge as Cawood Bridge is only manned between fixed hours in summer and by request in winter and the same for Naburn locks I do belive, not 100% certain
A good book I have read was about Selby in the old days when it had its own Custom House due to the large amount of foreign ships arriveing and loading and un-loading without stopping at other ports in the Humber.
[PDF] Selby's Railway Stations - Selby Town Council
www.selbytowncouncil.gov.uk/index.php/download_file/.../322/CachedSimilar
Starting on the Bawtry Road bridge, either go down the steps ... Wistow and
Cawood and as a bay for locos and carriages ... Such manned facilities were
once ... day on their way between London and Scotland. ... open causing several
minutes of delay to train services. ... wagons to be handled at any one time, with
further.
Very interesting leaflet abbout Selby Station area.
It does show the old interlaced tracks back in the East Coast Mainline days
which went across the bridge. Also it says about the changes to the Hydraulics in 1974 and the lifting of the bridge operators cbain in the 1980,s .