“客运量”常见的英文表达是 “passenger traffic volume” 或 “passenger volume” 。
passenger traffic volume：较为正式、专业，常用于交通统计、行业报告等场景，强调涉及乘客运输的业务量规模。例如：The railway department has released the passenger traffic volume data for the first half of the year.（铁路部门已公布上半年客运量数据。）
passenger volume：意思相近，表述更简洁直接，在日常交流、一般新闻报道中较为常用。例如：The passenger volume of this airport has increased significantly this year.（今年该机场的客运量大幅增长。 ）