IMO the ratio of DDs to SDs on 28 is alright. Its just that the
DDs and SDs slots deployment is all goofed up.
EG: 6.00 PM @ BDK twd tam. Its erm school dismissal time, buses
sure packed with students. Still deploy single deck.
7.10AM @ TAM twd TPY. Students catch this bus to make it to school
on time. Also another SD, next bus is a DD but by then the students
are late. 
IMHO Shortworking28A is the solution