It's not a bug. I asked support about it and got this response. They think it's fun everyone else finds it annoying.
Hello Mayor, thanks for contacting us.
To introduce new levels of fun, visible activity in your city we've been developing the road networks. There are 3 additional road levels now available in SimCity BuildIt. 'Level 4' roads feature tree-lined avenues with tourist buses; 'Level 5' has limousine-filled boulevards with your citizens strolling along the side walks; and on 'Level 6' you'll see street car avenues with trams on tracks and exciting new animations!
As each new road level relates to population density, if you already have a great many people living in your city you might see these new successive road upgrade requests sooner than would normally be expected. We appreciate this could be frustrating if you saw these all at once, so we've staggered each 'red' warning to minimise complaints from your citizens - there is now a "cool down" period between each 'red' upgrade request to give you time to react and gather what's necessary.
It's also worth noting that if citizens abandon a residential building for any reason (including lack of road upgrades), it's only a temporary state. They'll automatically move back in once normal service has resumed. So as soon as the roads are upgraded, they'll be back!
As commercial and industrial buildings also generate traffic, you might see these industrialized roads requiring upgrades too.
Thanks again for contacting us, and I'll be sure to pass your experiences on to our game team. Please let us know if there's anything else we can help you with
