1. The two express toll lanes, which will run along I-75 and I-575 in Cobb and Cherokee counties beginning in 2018, will be 30 miles long. The toll will be variable, depending on traffic.

2. The lanes will rise over and slip under the existing interstates, using 39 new bridges.

3. One of those bridges, at the interchange of I-75 and I-285, will soar 106 feet in the air, making it the tallest freeway bridge in the state – higher even than Spaghetti Junction.

4. The lanes will be reversible: inbound toward the urban core in the morning, closed at midday and then outbound in the afternoon. The state will use a series of signs and gates to direct traffic in the proper directions.

5. The $834 million cost of the project makes it the most expensive road project in state history. But not for long. The redesign of the Ga. 400/I-285 interchange will be even more costly.

Read the AJC's full report on the Northwest Corridor project and other toll lane projects to come in metro Atlanta.