As far as I know, bridges are currently not under heavy load. This is because not everyone connects via bridge. Moreover, even if everyone did, and nobody used onion services, the total bridge bandwidth should be exactly 1/4 the total bandwidth. Onion services require 5 (or is it 6? I think it's 5) public relays, so if everyone used bridges but everyone also used onion services then the bridge bandwidth should be 1/6 the overall bandwidth. But, as I said, the proportion of users connecting via bridges is much smaller than 100%.

As an aside, the ratio of counts is a poor estimate for the ratio of bandwidth, because bridges have much less bandwidth available on average than public relays.

Quoting Keifer Bly (2018-05-18 21:20:18)

Hello List,

There are some things I have noticed, I have been getting emails from this list regarding people setting up groups of new relays. I have also noticed that according to https://metrics.torproject.org/networksize.html, there are around 6-7 thousand public relays running in the network, and only about 1,500 to 2,000 bridge relays running (I’m guessing a fair number of which aren’t even obfuscated). Seeing as there is only roughly ¼ the number or bridges available as there are public tor relays, I think that it would be a good idea for new people running groups of relays to run one of their new relays as a bridge, especially with censorship growing in some countries such as the United Kingdom and even I’ve heard some US isps starting to block websites.

Please let me know what you all think, thank you.