So far, so good.

Tighter security requirements went into effect this week at U.S.- Canadian border crossings and traffic didn’t back up for miles – and hours.

Which is not to say that the Western Hemisphere Travel Initiative – part of the homeland security response to Sept. 11 – has come to pass without glitches. The requirement for passports or some form of enhanced ID was to have been in force for U.S.-Canada land crossings two and a half years ago, but political potholes kept forcing delays. Among them: the State Department’s failure to anticipate a flood of requests for passports.

The delays served a purpose. They allowed Washington and a handful of other northern tier states to develop scannable driver’s licenses as a more affordable alternative to passports.

Still, now that the world’s longest undefended border is under tighter security, it’s important to make sure that traffic will move as smoothly next week, next month and next year.

The 300,000 people a day who cross the border for work, shopping and recreation deserve that much. And it’s of major importance for the commercial traffic that’s worth an estimated $1.7 billion a day to the two neighbors’ economies.

That’s more than $1 million a minute, and, as Michael Wilson, Canada’s ambassador to the United States, has noted, serious border delays undermine competitiveness as fuel costs rise and retailers count on merchandise to arrive on a just-in-time basis.

Most Americans and Canadians get it that an unsettled world requires more security, even along their friendly boundary. But they expect controls to be imposed sensibly.

Passports, after all, are hardly fail-safe. The Sept. 11 terrorists had passports and visas. So did Ahmed Ressam, the Algerian ultimately convicted of plotting to blow up Los Angeles International Airport. It was his suspicious behavior that alerted the security guard who nabbed him bringing explosives into the United States at Port Angeles.

The real challenge, in the 9/11 Commission’s words, is to “check people efficiently and admit friends.”

The initial experience with stricter control over the U.S.-Canadian border is encouraging. But it needs continued monitoring, plus a willingness to make adjustments, as needed, to achieve the 9/11 Commission’s proposal for balance.