Great Western Coffee Shop

https://www.google.co.uk/maps/@52.6720363,5.0523774,3a,75y,264.92h,83.69t/data=!3m6!1e1!3m4!1sUuiu3NOQrddDgwvaIE5AyQ!2e0!7i16384!8i8192?coh=205409&entry=ttu&g_ep=EgoyMDI0MTAwMi4xIKXMDSoASAFQAw%3D%3D (https://www.google.co.uk/maps/@52.6720363,5.0523774,3a,75y,264.92h,83.69t/data=!3m6!1e1!3m4!1sUuiu3NOQrddDgwvaIE5AyQ!2e0!7i16384!8i8192?coh=205409&entry=ttu&g_ep=EgoyMDI0MTAwMi4xIKXMDSoASAFQAw%3D%3D)

Shows the N307 road in the Netherlands, where it is crossed by the Hoorn-Medemblik heritage line. This runs service once a day each way (twice in busier months).

The heritage line crosses another dual carriagway; it also has a large number of other level crossings, including one shared with NS trains.

Imagine the fits of the vapours at the ORR if a heritage line in the UK proposed to cross a major road in a similar manner

A heritage railway has recently done that. Getting approval from the ORR and Highways England to build a level crossing across an A road.

The Rother Valley Railway has its Transport & Works Act Order to build its line from Robertsbridge station to join up with the Kent & East Sussex Railway to the west of Bodiam station. The route includes three new level crossings, including one across the A21 Robertsbridge bypass.

https://www.rvr.org.uk/

https://www.gov.uk/government/publications/bodiam-to-robertsbridge-junction-order-transport-and-works-act-order

See to me the ORR should allow the level crossing in Portishead too then

The Welsh Highland Railway leaves the Harbour station at Porthmadog, shared with the Ffestiniog, then shares the high street (A497) over the Pont Britannia before leaving the tarmac behind on the 25 mile journey to Caernarfon. A really worth while trip, I suspect permission was granted because of the recently built bypass of the town.

It will all come down to a Risk Assessment, a heritage railway has a line speed of 25 mph, low frequency of rail traffic other factors will be is in a built up area with high level of pedestrians, the number of road vehicle; its quite an involved process 

My opening post was inspired by memories of this crossing of the A5 by the Oswestry-Gobowen route:
https://www.google.co.uk/maps/@52.8799055,-3.0396629,3a,75y,163.66h,66.38t/data=!3m7!1e1!3m5!1sorfHRxIvMQr_pJKui5iU6g!2e0!5s20240701T000000!7i16384!8i8192?coh=205409&entry=ttu&g_ep=EgoyMDI0MTAwNS4yIKXMDSoASAFQAw%3D%3D (https://www.google.co.uk/maps/@52.8799055,-3.0396629,3a,75y,163.66h,66.38t/data=!3m7!1e1!3m5!1sorfHRxIvMQr_pJKui5iU6g!2e0!5s20240701T000000!7i16384!8i8192?coh=205409&entry=ttu&g_ep=EgoyMDI0MTAwNS4yIKXMDSoASAFQAw%3D%3D)

I'm not sure if it would qualify as heritage these days as the rail route became the subject of an RYR application for a light rail service.

Note also Cholsey to Wallingford - https://www.cholsey-wallingford-railway.com/signalling/

I was involved with that railway in the 1980s and it faced a very real threat from the building of the Wallingford bypass.  Already truncated at the town end, it was facing the prospect of being cut in two with neither half likely to be viable. 

After much negotiation agreement was reached and the crossing installed.  I am aware of at least two incidents at the location since - neither resulting in serious injury - but in the main it has worked well.