- Bus-based Tunnel (and O-Train)
- Bus-Light Rail Tunnel (and N-S LRT)
- Light-Rail Tunnel (and O-Train; E-W LRT)
- Light-Rail Tunnel (and E-W; N-S LRT)
The costs, however, are nothing to scoff at. It's the second-most expensive option (Option One is cheapest at $3.16B, then Option Three at $3.37B, then Four at $3.82M, then Two at $3.87), but it also has the lowest operating costs once constructed and the lowest long-term environmental costs.
EDIT: Option Four is also the most in line with the report from the Task Force on Transportation, keeping in mind the following statement:
Canada’s capital city deserves a transit system that is enjoyable to ride, accessible, efficient, environmentally sound and developed in accordance with the principles of smart growth. Ottawa’s bus rapid transit (BRT) system has served the city well, but demand from current and anticipated growth requires more focus on light rail solutions.