|
                                |
                                |
                                |

                                 t
			                 /_ \
               	 	 	               s     a

                                                                            =
			                 /_ \
               	 	 	               P     

			                time
			                 /_ \
               	 	                                 P    space

				 t
			                 /_ \
               	 	 	               s     a


				|
				|
				|
				|
				|
				|
                                                                  P = Passenger