in droves

ニュージーランドでもいよいよクリスマスと新年の休暇がはじまります。渋滞はどこでも同じですが、人口400万人の国の半分程度の人々が、ちょうど羊が群れをなすように街を離れるのでその光景は壮観の一言です。in dorves、言い得て妙です。（Sugiuchi）
Warning to holidaymakers from police
By Michael Dickison
5:30 AM Friday Dec 23, 2011
Holidaymakers will start leaving main centres in droves this afternoon - and police will be watching closely as they try to keep the road toll at its 50-year low. Last year, 12 people died and almost 400 were injured on roads during the two-week Christmas and New Year holiday break.
http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10774975