以“1个人出行、10公里”为例（只比较使用阶段的温室气体排放）：
普通私家车（单人驾驶）：大约 1.6 kg CO₂e（约等于装满一只1.5升矿泉水瓶的“二氧化碳重量”）(DESNZ, 2025)。
城市公交（平均水平）：大约 1.25 kg CO₂e（通常比单人开车更省排放，尤其当车上乘客更多时会进一步下降）(DESNZ, 2025)。
国铁/城际铁路（平均水平）：大约 0.35 kg CO₂e（大约是单人开车的五分之一左右）(DESNZ, 2025; ORR, 2025)。
换句话说，如果你把每周两次10公里的单人开车改为乘轨道交通，一年累计的减排，往往相当于少开车上千公里的量级（取决于你原本的里程与出行频率）(DESNZ, 2025)。这些改变不需要等待“未来的科技”，今天就能发生：更高的公共交通使用率与更低碳的出行（含步行/骑行/公共交通）被认为是实现减排的关键“需求侧”路径之一 (IPCC, 2023)。
Q9 Please read the following message (MCQ: read confirmation)
Your travel choice can genuinely reduce emissions immediately.Using the example of a single person travelling 10 km (comparing only greenhouse gas emissions during the use phase):
A typical private car (single occupant): approximately 1.6 kg CO₂e (roughly equivalent to the “weight of CO₂” filling a 1.5-litre water bottle) (DESNZ, 2025).
Urban bus (average level): approximately 1.25 kg CO₂e (usually lower than driving alone, and emissions decrease further when passenger occupancy is higher) (DESNZ, 2025).
National rail / intercity rail (average level): approximately 0.35 kg CO₂e, which is roughly one-fifth of the emissions from driving alone (DESNZ, 2025; ORR, 2025).
In other words, if you replace two 10 km solo car trips per week with rail travel, the annual emissions reduction is often equivalent to avoiding driving over a thousand kilometres, depending on your original mileage and travel frequency (DESNZ, 2025).
These changes do not require waiting for “future technology” — they can happen today. Higher public transport use and lower-carbon travel options (including walking, cycling, and public transport) are widely recognised as key demand-side pathways for achieving emissions reductions (IPCC, 2023).
交通排放是气候与空气质量压力的重要来源，而且变化不够快。在英国，交通是最大的排放来源之一：仅“国内交通”在2022年就占英国国内温室气体排放的约28% (DfT, 2024)。在欧盟层面，交通排放占比在近年也处于接近三成的水平，并且减排进展相对缓慢 (EEA, 2024; EEA, 2025)。
与此同时，气候信号在“刷新纪录”：
世界气象组织确认2024年为有记录以来最热的一年，全球平均气温约比工业化前高1.55°C (WMO, 2025)。
Copernicus 与 WMO 的最新通报显示，2025年仍位列历史最热年份的前三，而近十多年几乎年年都在“最热榜单”里 (Copernicus, 2026; WMO, 2026)。
大气中的二氧化碳浓度也在上升。WMO 指出2023到2024年全球平均CO₂浓度增加约3.5 ppm，创现代观测以来的最大增幅之一 (WMO, 2025a)。美国官方气候科普资料也显示，2024年茂纳罗亚站年平均CO₂约为424.61 ppm，明显高于过去几十年的水平 (NOAA Climate.gov, 2025)。
简而言之：气候风险在累积、并没有“自动好转”；交通出行方式作为日常可改变的行为之一，正在被越来越多研究视为必须加速转型的领域 (IPCC, 2023; EEA, 2025)。
Transport emissions are a major source of pressure on both the climate and air quality, and progress in reducing them remains too slow.
In the UK, transport is one of the largest sources of greenhouse gas emissions. In 2022, domestic transport alone accounted for approximately 28% of the UK’s total greenhouse gas emissions (DfT, 2024). At the EU level, transport emissions have also remained close to around 30% in recent years, and progress in reducing emissions has been relatively slow (EEA, 2024; EEA, 2025).
Meanwhile, climate indicators continue to break records.
The World Meteorological Organization confirmed that 2024 was the hottest year on record, with global average temperature reaching around 1.55°C above pre-industrial levels (WMO, 2025).
Recent updates from Copernicus and the WMO also suggest that 2025 remains among the top three hottest years in recorded history, and the past decade has consistently been dominated by record-breaking heat (Copernicus, 2026; WMO, 2026).
Atmospheric carbon dioxide concentrations are also rising. The WMO reported that global average CO₂ concentration increased by around 3.5 ppm between 2023 and 2024, representing one of the largest annual increases in the modern observational record (WMO, 2025a). Official US climate data also show that the annual mean CO₂ concentration at Mauna Loa reached approximately 424.61 ppm in 2024, significantly higher than levels observed in previous decades (NOAA Climate.gov, 2025).
In short, climate risks are accumulating and will not improve automatically. As one of the most changeable everyday behaviours, transport choices are increasingly recognised as an area where rapid transition is urgently required (IPCC, 2023; EEA, 2025).