AAR

例句：

1. 1. The AAR is a standardized system for measuring the length of trains.
   AAR是测量火车长度的标准系统。
2. 2. The AAR requires all trains to be inspected before departure.
   AAR要求所有火车在出发前都要进行检查。
3. 3. The AAR has been instrumental in improving safety on railways.
   AAR在提高铁路安全方面发挥了重要作用。