SimCity Update 7 contains tool that create bridges, overpasses, and tunnels when you draw roads

The next update for SimCity will allow players to create bridges, overpasses, and tunnels while drawing roads thanks to a new tool.

According to a post on the official forums, when building your road, pressing the comma or period key will "lower or raise the road accordingly creating overpasses, bridges and tunnels."
However, existing road layouts cannot be raised or lowered.

Other improvements added include traffic behavior "to make it smarter," and reduce the number of lines formed by all available vehicles converging on a single spot.

This will affect all vehicles including: Police, Fire Trucks, Moving Trucks, Garbage Trucks, Recycling Trucks, Resource Trucks, Buses, Ambulances, and Civilian vehicles .

New tree tools will allow you to place individual trees around your city, and are located at the end of the Nature Parks palette.

Some fixes will also be implemented:

• Terrain: Fixes an issue some player’s see where terrain covers sections of roads while the camera is zoomed out.
• Fixed an issue where the fire animation would sometimes continue when fire was extinguished.
• Parks: Sports parks are now accepting Sims 24 hours a day.
• Airship: The number of Airship passenger trips should now be correct over multiple days.
• Vehicles: Vehicles now accelerate and decelerate faster, allowing them to leave buildings and go through intersections more efficiently.
• Freight: Freight trucks now only leave factories if they have a valid delivery destination.
• Gifting: Money gifting should be more reliable.

The update is currently being tested and should be rolled out soon.