Finally, more than 31 months after the last multi-year surface transportation law expired, House and Senate conferees sat down to begin working out differences between their two reauthorization bills. Construction industry and state transportation officials, who have had to endure nine short-term highway-transit measures since 2009, are rooting hard for a quick deal.

As expected, the conference committee's May 8 opening session, convened in the Hart Senate Office Building's imposing hearing room, didn't resolve much of anything. It was largely ceremonial, consisting of conferees' opening statements.

The conference chair, Senate Environment and Public Works Committee Chairman Barbara Boxer (D-Calif.), moved things along, allotting five minutes to committee and subcommittee chairs, and three minutes to the other lawmakers.

There are 47 conferees (14 Senate, 33 House) and most of them were there to speak their pieces. So this took a while. Total time elapsed: more than two and a half hours.

Now the real work will take place behind the scenes.

The Senate brings to the table a two-year $109-billion bill that it passed in March. The House brings a three-month bill  it cleared April 18, which has some significant non-highway/transit provisions attached. The most notable is a provision to speed approval of the Keystone XL oil pipeline. That isn't in the Senate version.

House and Senate staffers, who may well have already had preliminary discussions, will meet privately or communicate further to try to reconcile relatively non-controversial differences between their respective bills.

But the aides won't be able to settle everything. The tough issues will have to be handled by the conference committee's principals, including Boxer and the conference vice-chairman, House Transportation and Infrastructure Committee Chairman John Mica (D-Fla.).

If some topics prove especially difficult, they may have to be taken up by House Speaker John Boehner (R-Ohio) and Senate Majority Leader Harry Reid (D-Nev.).

Though partisan differences flared up from time to time at the conferees' initial meeting, the string of speeches was generally civil and cordial. At the end of the session Boxer noted that though lawmakers at times spoke with passion about various issues, "I heard no lines in the sand."

The clock is ticking. Boxer said that the conferees need to strike a deal by early June if the hoped-for compromise bill is to be enacted by June 30, when the current stopgap authorization runs out.