Summer of surprise standstills

The culprit: A concrete-pouring truck blocking the center carpool lane.

It was the second consecutive Saturday that overnight construction crews lingered too long on the highway, one of the state’s busiest roads, and was just part of a summer of unexpected traffic jams that have tied up travelers in the early morning, late evening, and other times when a smooth ride would seem a safe bet.

After years of dire reports about neglect of the state’s roads and bridges, state and federal construction money has flooded the roadways with construction projects that, combined with the quieter commutes of summer, have turned traffic patterns on their head, with tie-ups appearing seemingly out of nowhere. Traditional rush hour can be clear sailing, while a trip in the wee hours can turn into an endurance test.

“You leave the house at 5:40 [a.m.], and you’re still hitting traffic?’’ said Jay McQuaide, a corporate communications manager. “The last year for me, commuting between Andover and Boston, is the worst it’s ever been, much worse than the Big Dig construction years.’’

Work is ongoing on Interstate 93, north and south of the city and in the Big Dig tunnels. It will continue on the Tobin Bridge, on Interstate 495, on Route 2, on the Massachusetts Turnpike, and inside the Prudential Tunnel.

While most of the work on major roads is done at night, sometimes it starts early or runs over, as in the case of the Southeast Expressway tie-ups, which led to a reprimand of two private contractors.

Other times, as with the evening jams that have been stopping traffic on the Tobin, the back-ups are the result of a scheduled construction plan.

Calls to SmartRoute, the 511 traffic service, were up 12 percent in July, compared with the same month last year and at their highest volume since August 2007. That is often an effective way to judge how many people are stuck in clogged roads, said Jeff Larson, who runs the free phone and Internet service that alerts drivers to traffic delays.

In addition to construction, other more cyclical factors influence traffic jams. Car and truck travel, which had been sliding through most of 2008 because of high gas prices and a weak economy, has begun edging up again, according to the most recent state estimates.

Summer months in Massachusetts bring their own complexity. They are the busiest in terms of traffic volume. But because school is out and many commuters go on vacation, less of that traffic is concentrated in rush hour, increasing the likelihood of an off-hour tie-up.

“It’s painful,’’ said Joe Staub, deputy director of the Tobin Memorial Bridge, where a decking project has restricted lanes on and off since last summer. “And I understand it’s painful, because I’m in it.’’

The road network is a sensitive system, already near capacity, that redistributes in unexpected ways when disturbed, leaving alternate routes clogged, as well, explains Joseph Sussman, an MIT engineer.

Repairing roads after 8 p.m. makes the most sense because it has the least impact, he said. But if construction crews get off the road 20 minutes late or start 20 minutes early, as they often do, traffic can back up for hours, he said.

Highway and bridge officials seek a delicate balance when they schedule work. Cut daily hours back, and it will take more months to complete the project, adding costs as well as more long-term frustration for drivers. Work too many hours in a day or at the wrong time, and thousands of people can be stuck and angry.

Staub said he tries to keep workers from shutting down an additional lane on the Tobin on Friday nights, when many people head north to vacation spots.

But there are exceptions, when workers are in the middle of a concrete pour or rainy weather leaves them behind schedule. So the lower deck, which carries northbound Route 1 traffic, was down to a single lane one Friday night in June and another one in July, creating traffic back-ups.

Traffic planners also run into each other. The Tobin Bridge and I-93 have different management until a reorganization takes effect in January. The officials say they already cooperate, yet both major north-south routes have had lane restrictions this summer, leaving motorists with few alternatives when work begins sometime around 8 p.m. or 9 p.m.

“There’s traffic everywhere you look,’’ said David Bookbinder, a Peabody resident who recently spent an hour on the Tobin Bridge at about 11 p.m.

After more than five dormant years, state and federal money began pouring money back into the depleted network of roads and bridges two years ago.

Spending on the state’s main road and bridge program grew to a record $720 million in the fiscal year that ended June 30, a 38 percent increase over the previous year. The state will continue spending heavily on that program over the next few years.

Additionally, about $438 million in federal stimulus money will begin to play a larger role over the next two years, including 30 projects costing $180 million in the immediate pipeline. Add to that an eight-year, $3 billion state bridge program launched by the Patrick Administration last year, and the future looks quite dusty.

Luisa Paiewonsky, commissioner of the Massachusetts Highway Department, said there is no painless way to fix all the old roads and bridges that desperately need work, especially on busy roads like I-93, which carry hundreds of thousands of cars per day around Boston. Scheduling takes not only rush hour into account, but also vacation travel, she said.

“While I’m not in any way minimizing the traffic impacts,’’ she said, “the result of all this construction is going to be a much better state highway system.’’

Andrea Estes, Peter Schworm, and Jonathan Saltzman of the Globe staff contributed to this report. Bierman can be reached at nbierman@globe.com.