COUNTIF/SUMPRODUCT(?) to create a matrix from data

OK. I set up 6 Named ranges to make the formula look simpler. CTRL-F3 to view edit. They select the range of the table for each action needed in SUMPRODUCT.

They are all based on the use of INDEX;MATCH to select the column of the arrival time the column to the left of it and the column to the right of it (A_Rng0, A_RngMinus and A_RngPlus) and similarly for the departure time. The SUMPRODUCT then looks like this:

=IFERROR(IF(E$5<$D6,"",SUMPRODUCT((A_Rng0<>"")*(A_Rng0<>A_RngMinus)*(D_Rng0<>"")*(D_Rng0<>D_RngPlus))),"")

REMEMBER the Named Ranges MUST extend ONE column to the RIGHT of the last column with data.

N.B. You said: "the matrix shows four vehicles arriving at 0830 and leaving at 0915, whereas only three do (SD19, J333 and SL61)". In fact there are four. You forgot to count SH66.