Can anyone explain?

Dear all, refer to the attached website, the buses are just like railway and in the tunnels, can anyone explain why there's got such design and the benefit ? (except fast/reduce the chance in traffic jam?), I saw 2 MCW and 2 Tridents on the road too.

tks

http://www.citytransport.info/OBahn.htm

好似巴西0的3節掛接Volvo B58E都會經隧道的，
唔經隧道就好似國內BRT同台灣巴士專線用中間．
．．

成個網就係講漏國內同巴西．．．

[ 本帖最後由 3asv6 於 2008-5-19 01:11 編輯 ]