An intersection design that actually works -
Without the drama
The intersection of Key Highway and Light Street is totally inappropriate for a roundabout. Here's a simple design solution that actually works. Essentially, the two existing islands on Key Highway and Light Street would simply be enlarged to tighten up the intersection of northbound Light Street and the southbound left turn movement that crosses over it. This very tight intersection with minimum length pedestrian crosswalks would be controlled by a simple two-phase traffic signal. Pedestrians would cross Key Highway while Light Street through traffic moves, and would cross Light Street while Key Highway traffic moves - so simple even a BC-DOT employee could do it.
A third median island would then be constructed to totally remove southbound Light Street from the intersection. This island would start at Montgomery Street and extend as far north as desired. Essentially southbound Light Street would function as a quiet single-lane local service road with parking and any other appropriate desired traffic calming measures such as speed humps and "Stop for Pedestrians" pylons. It would also be possible to extend the southbound Light Street island separating "arterial" traffic destined for Key Highway and "local " traffic destined for Federal Hill as far north as Conway Street. While this would be an excellent way of minimizing the heavy traffic exposure on the adjacent land uses (Christ Church Apartments, Harbor Court Condos/Hotel), it would tend to make this seem like a permanent solution.
This design should be much cheaper than a roundabout. The railroad track wouldn't even need to be removed, unless the city wanted to. It would probably be preferable to keep this as cheap as possible, in keeping with the idea that it would only be temporary until the city comes to its senses and decides to create a more permanent solution with a narrower Light Street along the entire Inner Harbor.