All those tolls add up: From several digital dimes to pass through each U.S. 36 toll point to $9 or more to beat ski traffic on Interstate 70, Front Range drivers paid nearly $20 million to use Colorado’s growing express lane network in the first half of the year.

But the pandemic’s effects, including a transformation of commuting habits for many workers, reduced traffic in some of those lanes — and cut significantly into that money flow, which is still recovering.

The volatility has forced the Colorado Department of Transportation and Plenary Roads Denver, the private CDOT partner that manages U.S. 36 and connecting express lanes on Interstate 25 that go downtown, to dip into reserve funds as they’ve weathered the pandemic. Each draws on toll and fine revenue to make big debt payments on several highway expansion projects, along with covering road operating and maintenance costs on all toll corridors.

The pandemic’s effects have been especially clear on Plenary’s commuting-heavy segments as well as on CDOT-managed C-470, according to a Denver Post analysis of several years of monthly traffic and revenue data provided by CDOT and Plenary.

In the C-470 express lanes, which opened between I-25 and Wadsworth Boulevard in August 2020 — early in the pandemic — traffic has fallen 16% short of projections on average, according to CDOT’s Colorado Transportation Investment Office (CTIO), an enterprise arm that oversees several toll corridors.

Express lane numbers on C-470 and U.S. 36 have been on the upswing, The Post’s analysis found, with U.S. 36 toll-lane use up 61% in the first half of this year compared to early 2021, and C-470 up about 90%. But U.S. 36 was still below 2019 levels.

On some other corridors — especially the eastbound I-70 mountain lane and segments on I-25 north of U.S. 36 — the pandemic’s impact was much shorter lived, with leisure trips and weekend traffic recovering quickly. During the first five months of this year, express lane use on each of those corridors was up more than 10% over 2019 levels.

Asked if the lingering effects on some CDOT-overseen corridors’ revenue streams give any reason for heartburn, spokesman Tim Hoover said its leaders “don’t have any concerns about that, on any corridors.”

“We did see some declines during the heaviest and most intense parts of the pandemic,” Hoover said. “But there was a fairly rapid rebound, and the corridors overall have done pretty well. The one corridor that has performed not as well as expected is C-470.”

Losing a year’s worth of toll lane revenue

Overall, the express lanes brought in more than $34 million during 2021 — with about $22 million going to CDOT for its four segments and $12 million going to Plenary for its two.

Plenary manages U.S. 36 and the I-25 Central reversible express lanes to downtown as part of a long-term public-private partnership in which it also built one phase of the U.S. 36 expansion project between Denver and Boulder, completed in 2016. It pockets the toll revenue — and is responsible for paying off project debt.

Since the pandemic began in 2020, Plenary has had to eat revenue declines compared to 2019 that add up to $18.9 million in lost tolls and fines — nearly a year’s worth of income, The Post’s analysis found. That assumes Plenary’s 2019 calendar-year revenue would have stayed flat, rather than continuing to grow like it did in earlier years.

Christian Guevara, Plenary’s vice president of operations, said it still was able to keep up on debt payments.

“It’s definitely not easy — I’m not trying to say we coasted through,” Guevara said. “That’s kind of the (partnership) model and what we signed up for. Everything works both ways. While there’s upside, there’s definitely a potential for downside.”

A recent report from Fitch Ratings, which monitors Plenary’s ability to pay back $150 million in project debt, noted that it had drawn heavily on reserves set aside before the pandemic. It’s also continued raising toll rates each year to keep up with inflation.

For its part, CDOT’s opening of the C-470 lanes came nearly two years later than planned because of construction delays, requiring it to shift money to make early debt payments on borrowing that covered more than half of the highway widening project’s $276 million cost.

Hoover said the express lanes, while underused, are bringing in enough each fiscal year — $8.6 million in the year that ended in June — to roughly cover $8.1 million a year in payments, if not all expenses. But CDOT also has had to draw on corridor reserve accounts through the pandemic.

Fitch, in a separate report, upgraded its outlook on the project to stable and expressed optimism it will become self-sustaining.

“We’re not worried in the slightest about revenue declining or flagging,” Hoover said.

CDOT’s express lane network is growing

CDOT has expanded its express lanes network rapidly in the last decade — and it’s about to grow even more.

Its first segment was the reversible lanes running up the middle of I-25 from downtown to U.S. 36, which opened in 2006. In the last decade, five more corridors and segments have opened: on U.S. 36 all the way to Boulder, two more segments on I-25 from U.S. 36 north to E-470, on C-470 and on I-70 in the mountains near Idaho Springs (the westbound lane began tolling in July).

Some corridors’ express lanes include an HOV option, with U.S. 36 and I-25 waiving tolls for vehicles carrying at least three people as well as motorcyclists; the latter also are allowed on C-470.

While E-470 and the Northwest Parkway are full toll roads, CDOT’s express lanes are a different animal. They run next to the free general-purpose lanes and are called “managed lanes” by CDOT.

The idea is varying tolls at different times of day — more expensive during busy times — will entice some drivers with a paid option that allows drivers to zip past congestion. That’s also led some critics to call them Lexus or Cadillac lanes.

Those varying rates are lower for customers with ExpressToll transponders than for those charged by license-plate readers.

In a cash-strapped period for CDOT, express lanes also have helped finance major highway expansion and rebuilding projects worth $3.1 billion. Express lanes are open along 58 miles of highways now. Three projects underway will add more than 51 miles.

Early next year, express lanes will begin charging tolls along 10 miles of I-70 in northeast Denver and Aurora as well as on 18 miles of I-25 between Castle Rock and Monument; both are now in open testing. To the north, an expansion of I-25 between Berthoud and Fort Collins is adding express lanes.

How do toll lanes affect regular traffic?

CDOT and its CTIO enterprise point to data showing that its express lanes lighten congestion in the general lanes — even if modestly.

The eastbound I-70 peak-period shoulder lane, which opens only on weekends and holidays and now costs ExpressToll customers $8 to $9, has been in operation since late 2015. CTIO’s analysis of traffic congestion data last year for an annual report found that travel times on weekends had improved for all users compared to 2011 — by as little as 1% and as much as 46%, depending on the month and day.

Hoover knows many drivers are skeptical. Some would rather CDOT add a free-access lane, but he and other transportation experts argue that new free lanes eventually fill up as people take advantage of the extra capacity.

“The people who jump over to the express lane are people who take up less road space in the (general) lanes,” he said. “We think that there’s really solid established science on this, but it goes against the kind of — it’s counterintuitive to what many people believe.

“And the whole point of express lanes is to manage the traffic,” he said, “so that we are not simply locked into a policy of trying to build more road space as a way to address congestion. Our goal is to manage road space more wisely, and express lanes have been proven to work.”