The Federal Highway Administration is kicking off the public phase of its two-year study of the truck size and weight issue.

At Department of Transportation headquarters in Washington, D.C., on Wednesday the agency is hosting the first of four planned public listening sessions on size and weight issues.

Nearly 400 individuals are signed up to attend in person on through an online webcast of the event.

The other sessions are scheduled for next fall, winter and spring in preparation for the final report, due to Congress in November 2014.

The study, ordered by Congress in last year’s highway bill, will look at the safety and economic implications of changing the federal limits, including permitting 6-axle, 97,000-pound combinations.

It will compare trucks operating at current size and weight limits to bigger and heavier trucks on the basis of crash rates and other safety risk factors, as well as the costs of effective enforcement, and the impact of the equipment on pavements and bridges. It also will look into the impact on truck-rail competition.

The study is supposed to provide the factual underpinning of what ultimately will be a political decision on whether or not to reform the federal government’s size and weight standards.

The Wednesday session will solicit comments on which truck configurations the study should cover and where they might operate.

Three configurations already are included:

• today’s standard 5-axle, 53-foot, 80,000-pound combination,

• a 5-axle, 53-foot, 88,000-pound combination, and

• a 6-axle, 53-foot, 97,000-pound combination.

Other types up for consideration are twin 33-foot rigs, Rocky Mountain Doubles, Turnpike Doubles and Triples, as well as others the participants might suggest.

Also on the agenda are discussions of the data and analytical methods the agency should use in the study.

FHWA maintains a website that provides details on the progress of the study.