有3个网友回答
首先，火车自重很大。一般大家乘坐的客车一列重量在一千多吨。载重只有几百吨。一般路面无法承载如此大的压力。走钢轨是为了承载它的压力。
其次，火车的车轮是铁的，如果想高速平稳的运行，就不能在水泥地面，因为水泥地面还是很粗糙，并且容易破损，柏油地面则硬度不够。
再次，因为快,火车的车轮与铁轨之间的摩擦力小，提高了火车速度。
就这几个方面了，想不到别的了。
因为火车很重，有了铁轨，增大了受力面积，减小了压强
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