I-95 and I-278 are not concurrent here. Exit 54 is for access to 678 and 295; continuing on the main route will dump you onto 95 North where 278 ends. I-95 has anticipatory exits for 678 and 295 whose ramps merge with 278's exit 54, but the through routes are separate.
There is no direct access from 278 east to 95 south (or from 95 north to 278 west; that access is provided further west by the Bronx River Parkway or the Sheridan (which was actually downgraded from I-895 to NY 895)