There has been some ideas and tricks about building double-decker roads or bridges on the forum, so why don't we implement them as an official feature?
It'll allow us to add more road deckers rather than tricks. We'll use it with other featues while constructing roads like 'shift road's elevation' or 'keep the same road's elevation, and it also support ramps, diagonal roads and slopes, too!
With this feature, we won't need to use difficult tricks or waste area to create multi-decker roads, just click a button and build normally.
- may need this feature because it'll be really useful and convenient! If possible, could you add it into Theotown, please? I believe in your abilities! 
Best regards.