It's 8:30 a.m., late rush hour, and Jim Murphy has a multibillion-dollar set of new tunnels beneath downtown Boston at his fingertips. So far things have been quiet, but should traffic get gnarly, as it so often does in this city of six-hour gridlocks, his console will automatically display the problem areas. Then he'll have some options: Zoom in on the jam through closed-circuit cameras; direct traffic with variable message boards; and, if things take a turn for the worse, override local radio frequencies.