The main problem with a plan by the commonwealth of Virginia to partner with a private company to build a new Route 460 between Suffolk and Petersburg has always been the cost.

Even with the concession of allowing whichever private conglomerate builds the road to charge tolls ranging from $5.50 to $11 for cars (and even more for trucks), the only way to make it financially feasible has been to guarantee the state would put up a substantial sum — $500 million in the latest iteration of the plan — to help build the road.

Half a billion dollars is a lot of money for any highway, and even harder to get excited about when the highway in question would be under private control for the entire lifespan of just about every Virginian breathing today. Add to that the fact that anyone who wished to use the new link between Suffolk and Petersburg would have to pay a toll to do so, and it has been hard to understand sometimes why Gov. Bob McDonnell has made the new Route 460 the centerpiece of his transportation plan.

But McDonnell believes the new road is vital to the safety of Southeast Virginia and to the future economic viability of the commonwealth as a whole. Route 460 is one of the primary evacuation routes for Hampton Roads, but its current alignment and grade result in it being flooded during just the sort of events that could be expected to result in mass evacuations. A new road would take care of that problem.

Perhaps even more important is the fact that the current highway is too crowded to provide a safe, efficient way to transport goods to and from Virginia’s ports in Hampton Roads. And as the state builds new port capacity in Portsmouth and new warehousing and distribution centers spring up in Suffolk and Windsor, the problems with congestion along Route 460 will only get worse.

Considering how important the project could be for the Ports of Virginia, as well as the negative consequences that would ensue if shippers decided to take their cargo elsewhere along the East Coast, it only makes sense that the ports should share in the cost of the new road.

Apparently the Virginia Port Authority’s new board of directors has finally understood just what’s at stake. That board discussed this week a plan to contribute $5 million a year — up to $250 million — toward the project’s cost, starting in 2013, using funds it would have gotten from its share of the state’s Transportation Trust Fund. Members of the board are expected to discuss the matter in more detail at a meeting in October and vote on it in November.

Since there really is so much at stake for the Virginia Port Authority, buying in to the Route 460 project would be an appropriate move that would help ensure the long-term viability of the ports and of the businesses springing up to support them. And using money already earmarked for the ports to do so would help ensure that the project saddles Virginians with less debt. The new board of directors should approve the plan in November.