Engineering the Neural Automatic Passenger Counter

TL;DR

This paper enhances neural-based automatic passenger counting by exploring training strategies, ensemble methods, and novel quantization techniques to improve accuracy, reliability, and the ability to handle unbounded counts in public transportation systems.

Contribution

It introduces a comprehensive approach combining grid search, ensemble techniques, and Monte Carlo quantization to improve neural network performance in passenger counting tasks.

Findings

Ensemble quantiles reduce counting bias.

Training set size and initialization significantly affect accuracy.

Cumulative summation enables unbounded counting.

Abstract

Automatic passenger counting (APC) in public transportation has been approached with various machine learning and artificial intelligence methods since its introduction in the 1970s. While equivalence testing is becoming more popular than difference detection (Student's t-test), the former is much more difficult to pass to ensure low user risk. On the other hand, recent developments in artificial intelligence have led to algorithms that promise much higher counting quality (lower bias). However, gradient-based methods (including Deep Learning) have one limitation: they typically run into local optima. In this work, we explore and exploit various aspects of machine learning to increase reliability, performance, and counting quality. We perform a grid search with several fundamental parameters: the selection and size of the training set, which is similar to cross-validation, and the initial network weights and randomness during the training process. Using this experiment, we show how aggregation techniques such as ensemble quantiles can reduce bias, and we give an idea of the overall spread of the results. We utilize the test success chance, a simulative metric based on the empirical distribution. We also employ a post-training Monte Carlo quantization approach and introduce cumulative summation to turn counting into a stationary method and allow unbounded counts.