1. Look for sensible context in A1_Context                       1 mark
2. Look for sensible machine in A1_BasicMachine                  1 mark
3. safety - only one train in section                            1 mark
          - no following movements                               1 mark
          - no opposing movements                                1 mark
4. initialization                                                1 mark
5. 2 x leave events                                              1 mark
   2 x arrive events                                             1 mark
6. aesthetics                                                    2 marks
     - good, 2 marks
     - fair, 1 mark
     - poor, 0 marks