Route 1 is a storied highway, extending from the Canadian border in Maine to Florida’s southern tip. But as of last week, it’s no longer complete.

The 87-year-old Memorial Bridge, which carried Route 1 traffic over the Piscataqua River between Kittery and Portsmouth, N.H., is now a pedestrian-and-bicycle-only span due to severe deterioration.

That’s inconvenient for drivers, who now have to either detour to the high-level Interstate 95 bridge or use another street-level span.

But it could be catastrophic for businesses on both ends of the bridge. They had been planning on an 18-month closure while the bridge was replaced. Now, they may have to face one twice as long, because funding priorities mean replacement can’t begin until mid-2012.

That’s still good news in a way, because transportation planners had been considering not replacing the bridge at all, until Maine and New Hampshire officials worked out a way to afford the potential $300 million cost of fixing all three Piscataqua bridges. While it is possible that repairs could let the Memorial Bridge open again for some of the time before it has to be torn down, that’s not certain.

What is certain is that this bridge has been known to be in hazardous shape for years, and yet it could not be fixed or replaced in time to avoid this three-year hit on many businesses’ bottom lines.

That’s just poor planning, but it’s ordinary people, not planners, who have to pay the price for it.