Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK.
J Epidemiol Community Health. 2013 Aug;67(8):641-7. doi: 10.1136/jech-2012-202156. Epub 2013 Jun 13.
We used the introduction of free bus travel for young people in London in 2005 as a natural experiment with which to assess its effects on active travel, car use, road traffic injuries, assaults, and on one measure of social inclusion, total number of trips made.
A controlled before-after analysis was conducted. We estimated trips by mode and distances travelled in the preintroduction and postintroduction periods using data from London Travel Demand Surveys. We estimated rates of road traffic injury and assault in each period using STATS19 data and Hospital Episode Statistics, respectively. We estimated the ratio of change in the target age group (12-17 years) to the change in adults (ages 25-59 years), with 95% CIs.
The proportion of short trips travelled by bus by young people increased postintroduction. There was no evidence for an increase in the total number of bus trips or distance travelled by bus by young people attributable to the intervention. The proportion of short trips by walking decreased, but there was no evidence for any change to total distance walked. Car trips declined in both age groups, although distance travelled by car decreased more in young people. Road casualty rates declined, but the pre-post ratio of change was greater in young people than adults (ratio of ratios 0.84; 95% CI 0.82 to 0.87). Assaults increased and the ratio of change was greater in young people (1.20; 1.13 to 1.27). The frequency of all trips by young people was unchanged, both in absolute terms and relative to adults.
The introduction of free bus travel for young people had little impact on active travel overall and shifted some travel from car to buses that could help broader environmental objectives.
我们利用 2005 年在伦敦为年轻人推出免费公交旅行这一自然实验，评估其对积极出行、汽车使用、道路交通伤害、袭击以及社会包容度的一项衡量指标（出行总次数）的影响。
采用前后对照的控制研究方法。我们使用伦敦出行需求调查数据，在引入前和引入后两个时期分别对各出行方式的出行次数和出行距离进行了估计。我们分别使用 STATS19 数据和医院入院统计数据，对各时期的道路交通伤害和袭击发生率进行了估计。我们对目标年龄组（12-17 岁）的变化率与成年人（25-59 岁）的变化率进行了估计，并计算了 95%置信区间。
引入后年轻人乘坐公交车出行的短途旅行比例增加。年轻人乘坐公交车出行的总次数或出行距离增加，不能归因于干预措施。年轻人步行的短途旅行比例下降，但总步行距离没有变化。两个年龄组的汽车出行都有所减少，但年轻人的汽车出行距离减少幅度更大。道路交通伤害发生率下降，但年轻人的变化率比值高于成年人（比值比为 0.84；95%置信区间为 0.82 至 0.87）。袭击事件增加，年轻人的变化率比值更高（1.20；1.13 至 1.27）。年轻人出行的总频率保持不变，无论是绝对值还是相对于成年人的比例。
为年轻人推出免费公交旅行对整体积极出行的影响不大，只是将一些出行从汽车转移到了公交车上，这有助于实现更广泛的环境目标。
