State officials could soon fork over far more than expected for the next phase of widening Interstate 45, after bids on the next segment exceeded estimates by nearly $40 million.

Texas Department of Transportation officials estimated the project to make I-45 four lanes in each direction with two-lane frontage roads from north of FM 517 to south of FM 1764 would cost $191.4 million, based on early analysis. Total, the project was expected to cost $217.6 million.

Williams Brothers Construction, one of the region’s largest road builders, was the apparent low bidder when offers were opened Tuesday in Austin by TxDOT. The company’s bid was for $230.5 million, more than 20 percent higher than what was expected.

TxDOT officials said facets of an adjoining project and increases in fuel and construction material costs led to the higher bid, which still must be finalized.

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“We do not anticipate that variance between the original estimate and the final estimate will delay the award nor execution of the project,” TxDOT spokesman Danny Perez said.

Bids can often vary significantly from estimates, depending on when the estimate was made and changes in material prices. But a 20 percent difference is uncommon for a large freeway project, based on a review of the last six months of TxDOT bids.

In the Houston area, a $201.8 million project to widen Texas 146 in Kemah and Seabrook was 5.3 percent, or $10.3 million over estimates. A San Antonio area project to widen Interstate 10 to six lanes, bid at $119.8 million, was $6.9 million or 5.4 percent below estimates.

Material costs for road construction have increased slightly in the past year, according to the Highway Cost Index prepared monthly by TxDOT. The 12-month rolling average for reinforced concrete, for example, is at an all-time high, up 11 percent from last year and 20 percent since 2014, based on May prices.

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The work is the third project prioritized along I-45 as part of congestion relief efforts, given the growth along the corridor between Houston and Galveston and the freeway’s role as the main evacuation route from dangerous weather.

For many drivers, however, the freeway is the project that will never end, as widening or repairs have slowed traffic for more than seven years from the Sam Houston Tollway southward to Dickinson.

“I just want it over with,” said Ted Pitchford, 55, who lives in Webster and works in downtown Houston.

Still, a $40 million difference did raise concerns.

“That’s a lot of money to be off,” Pitchford said. “If I did that, I’d be fired.”

Dug Begley writes about transportation for the Chronicle. Follow him on Twitter at @DugBegley and Facebook at @PoppedClutchCity. Send him tips at dug.begley@chron.com

More Information Rising estimates Six companies submitted bids on the I-45 widening project, and all their offers were tens of millions of dollars above initial TxDOT cost estimates. Original estimate: $191,354,507.34 Williams Brothers bid: $230,477,520.47 (20.5 percent increase) Balfour Beatty: $244,938,856.58 (28 percent increase) Webber: $245,814,912.33 (28.5 percent increase) Johnson Brothers: $252,253,496.52 (31.8 percent increase) Pulice: $253,950,428.50 (32.7 percent increase) Fluor Heavy Civil: $257,957,252.52 (34.8 percent increase) Source: Texas Department of Transportation