Subway Carriage Density Awareness System
The Problem:
For my senior engineering thesis at Swarthmore College, I wanted to solve a problem faced by daily commuters. This led me to think about subway systems: these are often the most popular but also the most crowded of public transportation services. One problem commuters face is trying to avoid entering a crowded subway carriage. How could commuters be made aware of the more vacant carriages ahead of time?
The Ideating:
The problem ultimately boiled down to people-counting: what could be the most effective means to count density of people in a carriage, and relay this information to the platform? I brainstormed several routes, from thermal-imaging tracking warm bodies to pressure plates detecting footsteps. Ultimately I landed on break beam sensors that could detect direction of motion.
My hardware plan was thus to set up break beam sensors at the door of the subway carriage. Two distance sensors would be used to detect more than one person traveling through the doors. As the system counted bodies, the count value would be relayed to an external computer (on the platform) via wifi.
The Prototyping:
This proof-of-concept design required rigorous testing and constant debugging. The project had two major components: hardware and software:
HARDWARE:
Three pairs of break beam sensors were set up on opposite sides of a door frame. The order in which the beams were broken determined the direction of passenger motion. Distance sensors were added on each side to determine whether one or two people were walking through the door frame at once.
A NodeMCU wifi chip was hooked up to one side of the door frame to relay the data to an external computer.
SOFTWARE:
The code accounted for four possible scenarios of people entering or exiting the carriage. Scenario A: One person walking through; Scenario B: Two people walking opposite to each other; Scenario C: Two people walking closely behind each other; Scenario D: Two people walking side-by-side
The count value was posted on a webpage for an external computer to access on the internet.
The Results and Next Steps:
The final system successfully counted people according to the four scenarios listed. By integrating a wifi chip, the microcontroller was able to transfer the count data wirelessly onto a web server, thereby allowing the platform to access data of the carriage counts before the train reached the platform.
Moving forward, the system should account for more scenarios (eg. 3+ people walking through the doors). The count value should also be outputted to the commuters in some manner (eg. LEDs on the platform floor— red for full and green for vacant).