We’ve heard so long about spending more on transportation infrastructure that it may be hard to judge the impact and sufficiency of the bill approved this week.

So know this: The $900 million spending measure roughly doubles the state portion of our transportation spending. If you include federal money, the Georgia DOT budget will be about 50 percent bigger. That’s a huge step forward.

Decades of under-funding may have left a larger hole to fill, though that depends on who you ask. While raising up to $1.5 billion annually for “maintenance” became a common talking point during this debate, the DOT’s presentations to legislators outlined only about $600 million a year for projects such as repaving roads and replacing bridges. The rest of the “maintenance” money would be used for items such as adding capacity to existing roads and rebuilding undersized interchanges.

So there is money here for a fair bit of new capacity, especially if the money is managed well. But even if the need were closer to $2 billion a year, there is nothing wrong with taking one large step such as this and then waiting for the dust to settle before going further.

What’s more, the amount raised by House Bill 170 could be substantially more than $900 million. The final text included a provision to allow counties to levy their own version of the T-SPLOST that failed here in 2012.

That measure, in the metro Atlanta region, was projected to raise about $8 billion over 10 years. Depending on which counties add such a sales tax, and how much they levy (the bill allows for a fractional tax, up to 1 percent per county), that provision could generate hundreds of millions of dollars a year more.

But enough about the “how much.” What about the “how”?

This bill represents a sizable tax increase. There’s no getting around that. Some legislators who voted against the measure even deemed it the largest tax increase in state history. While I haven’t seen verification for that claim, it wouldn’t surprise me.

Still, that was going to be difficult to avoid when legislators have spent the better part of 30 years avoiding smaller steps that could have prevented this debate in the first place.

The bulk of the new money comes from raising the state portion of the gas tax to 26 cents a gallon from the current rate of about 19.3. If you drive 12,000 miles a year in a vehicle that gets 20 mpg, that’ll cost you $3.35 more per month.

You’ll also pay $5 more per night to stay at a Georgia hotel. Trucks and buses are assessed a fee of $50 or $100 per year, depending on their weight. Alternative-fuel vehicles will pay $200 a year (passenger) or $300 a year (commercial). A jet-fuel tax exemption goes away, hitting companies like Delta Air Lines, and a $5,000 tax credit for purchases of electric vehicles will also expire.

Those changes yield a total tax increase of about $720 million a year. The bill shifts about $180 million a year (the so-called fourth penny of the gas tax) from the general fund to the DOT budget. So about 20 percent of the new funding comes from existing revenues.

Could I have drafted a bill I liked better? Sure. And voting for tax increases need not become a Gold Dome habit.

But on the whole, I think this is a reasonable way to address what has for too long been neglected as a priority.