Should it be possible to place a diagonal filter on a main road?

At #18.04/55.955162/-3.14336 in Edinburgh. This "dog leg" intersection is now transformed to a 4-way intersection, so it's almost a candidate for a diagonal filter. But due to https://github.com/a-b-street/ltn/blob/e5e5735d608c728b679c00dee25b5a4aa4e4df4b/backend/src/neighbourhood.rs#L241, the user has to reclassify as a local road before considering a diagonal filter. This is inconsistent with how we allow main roads to have regular modal filters at a point. What was the reasoning for this?

该 issue 引用了 backend/src/neighbourhood.rs 中的一行代码，该行代码阻止在主干道上放置对角过滤器。首先检查第 241 行附近的逻辑和周围代码，以了解这一限制。将其与普通模态过滤器如何被允许放置在主干道上的情况进行比较。确定这一限制是有意设计的，还是一种不一致，并考虑要允许在变换后的交叉路口的主干道上放置对角过滤器，需要进行哪些更改。

由索引模型根据 Issue 内容生成。