void add_turnout(Turnout &);
Turnout &get_turnout(unsigned) const;
void add_locomotive(Locomotive &);
Locomotive &get_locomotive(unsigned) const;
void add_sensor(Sensor &);
Sensor &get_sensor(unsigned) const;
void add_turnout(Turnout &);
Turnout &get_turnout(unsigned) const;
void add_locomotive(Locomotive &);
Locomotive &get_locomotive(unsigned) const;
void add_sensor(Sensor &);
Sensor &get_sensor(unsigned) const;