> For the complete documentation index, see [llms.txt](https://www.oulan.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.oulan.com/2020/03/04.md).

# 04

在路边安装栅栏有两个作用。可以有更高的速度，可以限制速度。

![](/files/QqfTRTMamK8hBqRs2WRE)