Semaphore:  admin=1;  board=0; car=0; unboard=0.
Counters:  nr=0; nrw=0;

PASSENGER:

P (admin);
if (nr==C) {nrw++; V(admin);P(board);}

//Now I need to board
nr++;
if (nr==C) {
 V (car);
 V (admin);
} else if (nrw > 0) {
 nrw--;
 V (board);  //I'm passing the baton to the next boarder.  That guy is now in charge of the admin semaphore
} else {
 V (admin);
}
P (unboard);
nr--;
if (nr > 0) V (unboard); //passing the baton
else if (nrw > 0) {nrw--; V (board);} //passing the baton to the boarders
else V (admin);

CAR

while (true) {
 P (car);
 drive around
 P (admin);
 V (unboard); //passing the baton
}