the whole song goes 4 counts of d then four counts of d without the second finger(x2) 
then 4 counts of a then four counts of a and then 4 counts of a7. repeat through the whole 
song. the d variation will be called d<

ROCKIN ON THE BUS

(chorus)
D
rockin on the bus
D<
rockin on the bus
D
the wheels are rocking
D<
and there aint no stoping
A
while were rocking on the bus

riff-A7,A,A7

D
rocking down the street
D<
cranking out the jams
A
i open up the door
A<
and makes a big ole slam
A                      A7
if you wanna rock with me
A                   A7
then get on the bus and grab some seat

(chorus)

D
just pull up a seat
D<
get comfortable
D                     D<
cause we'll be rockin for a while
A                   A7          A    A7
we'll be rockin for hundreds of miles

(chorus)(x3)