SALT LAKE CITY — Transportation Secretary Norman Mineta visited shippers in four states on a pair of day trips this month aimed at highlighting the effect of congestion on U.S. business and advocating the Department of Transportation’s plan to ease the nation’s jammed transportation network.

The Federal Motor Carrier Safety Administration proposed changing the formula that it uses to run its SafeStat carrier rating system, alterations that may change the fleets identified as posing a crash risk.

The Department of Transportation’s internal watchdog office said the Federal Motor Carrier Safety Administration is not doing enough to stop carriers who repeatedly break federal safety rules.

The Department of Homeland Security said last week it has started conducting background checks on hundreds of thousands of port workers, the first step in unveiling the Transportation Worker Identification Credential, commonly referred to as TWIC.

The National Transportation Safety Board has again called for the installation of collision avoidance technology on new large trucks following its investigation of a 2003 accident that involved a tractor-trailer and several passenger cars at a toll booth in Illinois.

Several truck and brake manufacturers disagreed sharply with safety advocates over how much the Department of Transportation should cut heavy-truck stopping distances, with the manufacturers preferring a less-drastic reduction while another brake maker and safety groups pressed for shorter distances and mandated disc brakes.

The long-awaited intermodal chassis safety rule from the Federal Motor Carrier Safety Administration was undergoing the final stages of a review last week before being sent to the Office of Management and Budget, a spokesman for the agency said.

Attorneys representing Public Citizen filed a motion asking that its challenge to current hours-of-service rules for truck drivers be judged by the same panel that overturned the prior regulation.

A pair of trucking groups urged the National Highway Traffic Safety Administration to take another look at proposed changes to its rules on vehicle lights and similar equipment.

An official with the Department of Homeland Security told a shipper group that the agency plans to introduce a single identification card for transportation workers later this year.