virtual unsigned add_loco(unsigned a, const std::string &, const VehicleType &) { return a; }
virtual void remove_loco(unsigned) { }
virtual void set_loco_speed(unsigned, unsigned);
virtual unsigned add_loco(unsigned a, const std::string &, const VehicleType &) { return a; }
virtual void remove_loco(unsigned) { }
virtual void set_loco_speed(unsigned, unsigned);