after only six months,traffic coming into central London was reduced by about 30 percent,

问题描述:

after only six months,traffic coming into central London was reduced by about 30 percent,
and journey times by 15 percent.这里的times 被翻译成时间,为什么要加s

time 也有"次数"的意思,这里的journey times就是表示"出行的次数".
全句的意思是:6个月后,伦敦中心的交通流量减少了30%,(人们的)出行次数(也可理解为"频率")减少了15%.
..