This week's Good Facility is an example of a British 'underpass' done well, in the city of Glasgow.
Underpasses have a bad reputation, principally due to poor visibility and lack of clear sightlines - this example, however, is largely open to the elements and has clear visibility throughout. It is also well-lit at night.
Large motorways like the M8 certainly shouldn't be built so close to city centres, as in this case, but this is nevertheless a good example of how it is possible to design good crossings for walking and cycling.