The Benefit:Cost ratio of 2.90 (see the Appendix, Table A12) indicates a very good scheme, and the cost per new transit rider is only about $5,600. Moreover, the scheme can be implemented with less disruption than any of the current schemes. The Sheppard subway would need to be closed for a few months to modify track and signalling, but no major changes would be required to stations. There would be no need for an extended closure of the Scarborough RT, as the replacement terminal at Kennedy would be built on a different site. There would be much less disruption to traffic on Sheppard Avenue. The elevated line along 401 could be constructed mostly at night, so some overnight lane closures would be required as they are now when repaving work is under way.
This scheme could be described as a subway extension, as it would indeed be an extension of the Sheppard line and would offer the quality of service that is associated with a subway. Of course, if the Markham GO line is upgraded to offer a “metro” service, there may be no need to rebuild the Scarborough line south of Ellesmere. The Scarborough line could simply be joined into the Sheppard Subway, offering a direct “subway” from Sheppard-Yonge to Malvern via Scarborough Centre, with interchange to the Markham GO line at a new station east of Kennedy and north of Ellesmere Road. With travel times of about 30 minutes to Union Station, GO would offer much faster connections to downtown, and indeed through to emerging employment centres elsewhere in the GTHA, and at much lower cost than extending the subway.