Maximum slope values should not differ too much from reality as it affects walking/cycling/wheelchair accessible routing.
Maximum slope values differ noticeably from reality and therefore, wheelchair accessible routing is enabled/disabled on edges when it should not be.
compare maximum slope values against what streets look like on google street view, for example.
Maximum slope values for edges do not seem to correlate well with reality. In some cases these values are too high and in some cases they are too low.