Question

at/on/by the side of the road 什么区别

Answer 1

at the side of the road意思是 在马路边
on the side of the road意思是在路的一边
by the side of the road意思是在路的旁边

例句
Left for dead by the side of the road two years ago, it has quietly rehabilitated itself and now stands as 2011 's most accomplished full-line manufacturer.
就在两年前，克莱斯勒（Chrysler）还被抛在路边等死，但现在它已经悄悄恢复了元气，洗心革面，一跃成为2011年最成功的全线汽车厂商。

Pictures posted online show flayed dogs, dogs hanging from meat hooks, and piles of dog corpses on the side of the road.
网上曝光的照片里有被剥皮后的狗、挂在肉钩上着的狗、还有路边上成堆的狗尸体。

He was knocked out by a stone hurled at him from the other side of the road.
他被马路对面向他投来的一块石头打昏了。

Answer 2

at the side of road在路旁
on the side of 拥护的意思 I am on the side of you.
by the side of 在...附近 应该是by一个意思。
在边应该可以用by 和 at

Answer 3

at the side of the road ， 路上的一处固定地点，介词 at 强调 地点，可以加左右方位；
on the side of the road，一条路的上面，介词 on 强调 路上；
by the side of the road ， 在路的旁边，介词 by 强调路边；
at the side of the road与by the side of the road没有太大区别,
一个可以翻译成“在路旁”；一个是“靠路边”,介词的选择取决于前面的动词和语境。
例句：
1. I'm standing by the side of the road and waiting for a taxi.
我正站在路边等出租车。
2. Look，there is an accident at the left side of the road.
看，路的左边有一起事故。
3. He is walking on the side of his favourite road.
他正走在他最喜欢的路上。