The 78 acts as a supplemental route to the 8 which is why it has horrible headways.
The BL-4 on Sunday is horrible, mainly because the last bus from Bedford Park leaves at 8 PM. It used to be 7 PM.
On Sunday, there is a 1T variant that operates but ends at Dobbs Ferry, but uses the 1T designation. Not sure why it doesn't use the regular 1 designation, but there's been confusion brought up to the county that there's no difference between the City Line & Dobbs Ferry signage.