Back in black? Depends on how you define the baseline.

In the first three months of operation, express toll lanes on I-405 brought in $3.7 million in toll revenue — three times the conservative $1 million estimate used for planning by the Washington State Department of Transportation.

That’s more than enough to cover the costs of operations so far.

But some key expenses have yet to kick in.

And while there are a lot of zeroes in that figure, tolling revenue is hardly a windfall (so far).

To put it in perspective, the overall $2.7 million net revenues is only a fraction of the total $463 million price to expand the highway south of Highway 522 and install toll equipment in the first place — 0.58 percent, to be precise.

At that pace, it would take over 40 years to pay off an equivalent project.

The vast majority of that $463 million was for various widening projects along the corridor. The tolling part of the project was $111 million, about 24 percent of the total. If we look only at the tolling portion of the project, toll revenues at the current pace would pay off the project in about a decade.

In the long run, that’s not insignificant.

Tolling adds another stream of revenue to back the long-term debt payments required for major projects.

Tolling revenue from I-405 is kept in a separate account to be used on I-405 projects.

First up is expanding toll lanes south, for a total of 40 miles, to connect with similar lanes on Highway 167 south of Renton. A little over 18 percent of the total $1.1 billion cost of that project is expected to be covered by toll-backed funds. The rest comes from traditional funding sources, including the gas tax.

That all assumes the Legislature doesn’t dump tolling after its first two years, of course.

And operating in the black isn’t the only standard of success if you’re a commuter stuck in traffic that’s worse than before tolls.

If traffic doesn’t improve, opponents promise they’ll keep hacking away at “the snake oil of congestion reduction.”

Read more about the current financial statement for the toll lanes and how to understand them on the WSDOT Blog, at wsdotblog.blogspot.com.

Have a question? Email us at streetsmarts@heraldnet.com. Please include your first and last name and city of residence. Look for updates on the Street Smarts blog.