Last week, we brought you the first three of our (reverse order) picks for the top trucking-related stories and trends of the past year. Today, the next three on our list of 2012's biggest news:

7. Navistar Retrenches

The troubled truck and engine maker dominated the top viewed stories on in 2012, taking up 10 of the top 25 spots.

After several years of trying to come up with what it said was a better way to meet EPA 2010 regs, Navistar International in July announced it would add urea-based aftertreatment to its engines. In December, it announced it is shipping to customers its first 300 International ProStar+ Class 8 on-highway tractors equipped with the Cummins ISX15, ahead of schedule.

After "unacceptable performance" in its first-half results, Navistar announced management changes, with Troy Clarke, president of Navistar Asia Pacific, assuming responsibility for all Navistar's operations in the newly created role of President, Truck and Engine. Jack Allen was named president of North America Truck and Parts, an expansion of his current role. Later in the year, Dan Ustian retired as chairman, president, and CEO, and Lewis B. Campbell, former chairman, president, and CEO of Textron Inc., was named executive chairman of Navistar's board of directors and interim CEO. Most recently, Jim Hebe, senior vice president, North America Sales Operations, announced his retirement in October.

In August, Navistar invited trucking journalists to its Lisle, Ill., headquarters to share the thinking behind the change to SCR.

"The only thing we ran out of here was time," Allen said. "We ran out of credits before we could get to 0.2."

Company officials have been working to cut costs and streamline the company, and this year has announced it's closing its Garland, Texas, truck plant, shutting down the Workhorse operations it bought a few years ago, divesting itself of its Indian joint venture with Mahindra.

In December, the company reported a worse fourth-quarter loss than expected, thanks in part to a spike in warranty costs along with the weakened truck demand affecting all truck makers.

6. Natural Gas

Search for "natural gas," and you'll see more than 250 results for 2012, more than twice as many as 2011.

In March at the Mid-America Trucking Show in Louisville, Ky., it seemed nearly every press conference had an announcement related to natural gas.

By late November, when the American Trucking Associations convened its first Natural Gas Summit, it ended up with a crowd about twice what it initially estimated.

While adoption is still slow, two key trends have occurred this year that help address the chicken-or-the-egg question from both sides. Engine makers have announced that there will be a larger variety of natural gas engines available, and natural gas suppliers have made major investments in creating a natural gas fueling infrastructure.

5. Driver Shortage

The driver shortage did not become the crisis many had expected in 2012, due to sluggish economic growth.

Nevertheless, the annualized linehaul driver turnover rate at large truckload fleets remained over 100% for the second straight quarter in the third quarter, and the churn at smaller truckload carriers rose to a five-year high, according to American Trucking Associations Trucking Activity Report.

In November, ATA released a report saying the current shortage is acute and limited primarily to the truckload sector of the industry; but that long-term trends could cause the shortage to explode in the next decade.

Tomorrow, Part 3