BANGOR, Maine — As ground slowly recovers from its frozen winter slumber, it saturates with water, causing the ground to weaken and putting the road that runs above it at risk. Add 60,000 pounds or more to a road with a weakened substructure and you could have a big problem.

“If you walk on a gravel road right now, it’s soft, your feet will sink in,” explained Cliff Curtis, a highway maintenance engineer with the Maine Department of Transportation. “If you walk on the same road in the summer, the ground is tightly packed. It’s more structurally sound.”

That’s the thought process behind posting weight limits on state and local roads in Maine, an annual rite of spring that helps keep heavy trucks from damaging fragile roads. Road posting already has begun in many parts of the state and is likely to continue through most of March and April.

Aside from the practical reasons, there is a fiscal incentive for posting roads. It’s monumentally less expensive to keep heavy trucks off roads for a short period of time every spring than to let those vehicles pass and risk significant damage.

“When you look at replacing roads, that’s $1 million a mile,” MDOT spokesman Mark Latti said. “We’re protecting state investments.”

MDOT posts state roads at a 23,000-pound weight limit but makes exceptions for trash pickup, heating oil deliveries, school buses and other essential traffic. At peak, Latti said, approximately 2,000 of the state’s 8,500 roads could be posted.

Bangor Public Works Director Dana Wardwell said Bangor, and most other municipalities, set guidelines that mirror what the state sets out. He said his employees have begun posting roads in the Queen City, mostly in rural areas such as Essex Street, Ohio Street, Finson Road and other streets away from downtown.

“Once we start to see running water, that’s a telltale sign,” he said. “Our roads are marginally built to handle the weight anyway, so to allow them when there is a lot of water could spell disaster.”

Temperature is the deciding factor on road posting and when the temperature hovers above 32 degrees, even in overnight hours, MDOT officials will start the process. February was one of the warmest and least snowy on record, according to National Weather Service meteorologists in Maine, which suggests the process might be slightly ahead of schedule. The average temperature for February in Bangor was the third-highest on record, at 7.5 degrees above normal and Caribou was nearly 11 degrees above normal.

However, although the mild weather of the last few days has many yearning for spring, meteorologists warn that temperatures could cool back down in the latter part of March and perhaps bring more snow.

Road postings typically last until mid- to late April, but that could change with an excessively wet spring, according to Brian Burne, another MDOT engineer.

“Every year we evaluate our roads. There are always sort of classic roads that we post, but when we observe some destruction that wasn’t there before, we’ll do outreach,” he said. “We also realize that our economy is based on trucking, so we try to keep [roads] posted as short a period of time as is necessary.”

Burne said the process of posting roads is painstaking but important.

“Bear with us,” he said. “This is one of those necessary evils that we have.”

A list of posted state-owned roads can be found online at Local road postings can be found by calling or visiting municipal offices.