It is occasionally and erroneously stated that underpasses are unsafe and difficult to build. However, underpasses are already used safely and successfully in Horsham, e.g. the North Street Subway, the track to the Horsham golf club and also the newly created tunnel under the M23 at Handcross. All are safe and not intimidating when properly designed and maintained. It is even possible to install an underpass over a single weekend, as seen in the following timelapse video of the A12 near Arnhem in the Netherlands.
https://www.youtube.com/watch?v=btOE0rcKDC0
” It is even possible to install an underpass over a single weekend…” not to mention the strong wind and rain – impressed!