There isn't an official limit on the number of layers you can have in your map. It depends on a number of factors, including how much your browser can handle, your hardware (desktop/laptop/mobile device), network latency, how large your layers are, etc.
The larger the layer, the heavier the payload in querying for that data. That also means a lot of smaller layers can add up too.
Can you describe the content of the 54 layers? Are you using them for reference? Editing? Do they represent completely different data for overlay purposes, or do they represent similar features? Based on your snippet above, I figure it's a transportation app. Are they all lines representing road features, or does it include a lot more than that?