[gtasarules14]

public OnPlayerEnterVehicle(playerid, vehicleid, ispassenger)
{
new v = GetPlayerVehicleID(playerid);
if(v = your vehicleid)
{
if(PlayerInfo[playerid][pAdmin] > 1)
{
SendClientMessage(playerid, -1, "You are not a Admin");
RemovePlayerFromVehicle(playerid);
}
}
return 1;
}

This is my accurate bet , and these guys wrote it better than me lol