## 4 Result Analysis and Comparison with FTA
### Improvement on Control Process  
In the event of an accident, the impact on the individual or society is enormous. The complexity of the system and unreasonable control process, even the tiny design error, play an important role during the emergency situation. Due to the different perspectives to understand hazards and accidents, some inherent flaws can be hidden for a long time. From the above-mentioned description of hazard analysis of escalator brake system, some improvement measures can be added in the controlled process to prevent accidents or improve emergency response capabilities of EEBS.  
Figure 15 shows the improved controlled process. Pink lines and dashed boxes indicate added control paths that may improve system safety.  
(1) Passengers, as the primary carrier of the escalator, should be fully utilized to know and protect themselves during the boarding time in case of emergency.  
(2) A manual switch for emergency brake not for driving brake is very important in case of state judgment error of automatic emergency brake trigger. In fact, in most escalator reversal accidents, the automatic emergency brake was not triggered is one of the main reasons for the accidents.  
(3) Passenger needs an effective way to sense the speed information to make the right response. Another improvement measure is that a spare emergency brake is necessary to help and share the huge impact energy of mechanical friction when the emergency brake is working.  
(4) Necessary traffic flow monitoring and control measures should be added to adjust the heavy load during long working time. Then, necessary feedback which can reflect brake information (such as brake time, brake distance, brake force etc.) can be added to the system. This feedback path can record the processing capacity of the braking system in emergency situations and will have important reference value for the design and improvement of the brake.  
In fact, the above-mentioned improvement measures have a good practical significance for design and manufacture of EEBS. For example, over-reliance on broken chain detection (BCD) of anti-reversion device is an obvious casual factor for reversion accidents. So, a new trigger mechanism needs to be designed to trigger the anti-reversion protection device. Perhaps environmental decibel detection or vibration monitoring of key driving components could be a good choice. When accident happens, many people around the escalator including the passengers will make a scream or call for help,  
Figure 15: Improvement to escalator brake process.  
which would significantly increase the decibel value of the environmental voice. When environmental decibel value reaches a certain threshold, the trigger can act timely. Or a vibration sensor for condition monitoring of key driving components can also help to trigger the anti-reversion device when abnormal vibration information appears during accident period. It should be noted that the new trigger mechanism here is only an auxiliary protection device and does not replace the original basic protection principle based on BCD. Here we give a more concrete solution to the above-mentioned BCD, environmental decibel detection and vibration detection to solve the anti-reverse device triggering in Figure 16. We hope to use some comprehensive triggering conditions to reduce the possibility of misjudgment by a single trigger. Therefore, by collecting the signal detected by BCD, the sound signal detected by environmental decibels and the vibration signal of key components, and then using signal processing methods to judge the true state of the escalator reflected by above information, and then logically controlling whether or not to determine to trigger the anti-reverse device. The logic control algorithm here requires a lot of experimentation and data analysis. Here is just a way to solve the above-mentioned improvement measures in a practical way, and specific devices or algorithms require extensive experimentation and validation in the future.