Carbon Dioxide Concentrations and Temperatures within Tour Buses under Real-Time Traffic Conditions.

Chun-Fu Chiu,Feng-Hsiang Chang,Ming-Hung Chen,Jeffrey Shaman

doi:10.1371/journal.pone.0125117

Chun-Fu Chiu, Feng-Hsiang Chang + Show 2 more

Open Access

https://doi.org/10.1371/journal.pone.0125117

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Abstract

This study monitored the carbon dioxide (CO2) concentrations and temperatures of three 43-seat tour buses with high-passenger capacities in a course of a three-day, two-night school excursion. Results showed that both driver zones and passenger zones of the tour buses achieved maximum CO2 concentrations of more than 3000 ppm, and maximum daily average concentrations of 2510.6 and 2646.9 ppm, respectively. The findings confirmed that the CO2 concentrations detected in the tour buses exceeded the indoor air quality standard of Taiwan Environmental Protection Administration (8 hr-CO2: 1000 ppm) and the air quality guideline of Hong Kong Environmental Protection Department (1 hr-CO2: 2500 ppm for Level 1 for buses). Observations also showed that high-capacity tour bus cabins with air conditioning system operating in recirculation mode are severely lacking in air exchange rate, which may negatively impact transportation safety. Moreover, the passenger zones were able to maintain a temperature of between 20 and 25°C during travel, which effectively suppresses the dispersion of volatile organic compounds. Finally, the authors suggest that in the journey, increasing the ventilation frequency of tour bus cabin, which is very beneficial to maintain the travel safety and enhance the quality of travel.

Highlights

Traffic accidents are the primary cause of injuries and fatalities among tourists during leisure travel [1]
In Taiwan, a 43-seat tour bus usually carries between 30 and 40 passengers, suggesting the possibility of even higher CO2 concentrations. These results showed a severe lack of ventilation in commercial buses especially under heavy occupancy conditions, leading to concerns as to whether bus drivers are influenced by the poor air exchange rate and elevating the risk of traffic accidents; besides, the factors that increase the CO2 concentrations in vehicle cabins include mainly more passengers onboard [11,12,13,30], lower driving speed [12,13,30], and setting the air conditioning (AC) system to recirculation mode [12,13,14]
Using the AC system may reduce mileage by 5–25% [37], the need to reduce energy consumption provides an incentive for low rates of ventilation, leading to higher indoor CO2 concentrations [28]

Summary

Introduction

Traffic accidents are the primary cause of injuries and fatalities among tourists during leisure travel [1]. Hsu and Huang [30] monitored the air pollutant concentrations aboard buses travelling long distances on the highway and indicated that the average CO2 level is 1463 ppm, which is higher than the guideline for nonindustrial occupied settings [30]. Especially under heavy occupancy conditions, leading to concerns as to whether bus drivers are influenced by the poor air exchange rate and elevating the risk of traffic accidents; besides, the factors that increase the CO2 concentrations in vehicle cabins include mainly more passengers onboard [11,12,13,30], lower driving speed [12,13,30], and setting the air conditioning (AC) system to recirculation mode [12,13,14]. The present study endeavored to collect CO2 concentration and temperature data for 43-seat tour buses to serve as a reference for relevant authorities and vendors to improve travel safety

Methods

Results

Discussion and Conclusion