After spending $18 million and 18 months to overhaul the busy stretch of Sir Francis Drake Boulevard between Kentfield and Highway 101, you would think the job was done.

Not yet, as the county is now working on a costly “re-do” of parts of the project.

First, the county’s installation of new street lighting drew residents’ complaints that it was too bright.

The county has been working to remedy that problem. A $729,000 overhaul of the lighting is expected to begin this spring, having been delayed by problems getting the necessary supplies.

Now, the fencing that separates the sidewalk from the traffic is drawing complaints that it isn’t enough to protect pedestrians or bike riders.

The county replaced a metal guardrail with a much more attractive and taller post-and-cable fence. The fence was designed to prevent pedestrians from jumping it and getting into traffic lanes, but it has proven more flimsy than the guardrail when it comes to protecting pedestrians from traffic.

Since the new fence was installed, in its short span, five hit-and-run accidents have damaged sections of the fence, costing the county more than $46,000 to repair.

That’s more than $9,000 per repair, which would be a costly ongoing expense.

That damage is evidence that it may be only a matter of time before the fence is tested when there is a pedestrian or bicyclist on the path.

County officials are weighing the options, stressing that public safety is “the first priority.” That is a must.

Officials plan to provide an update on their progress this month.

The long-debated project, the construction of which took 18 months and routinely slowed traffic on Drake, has turned out to be more of a work in progress, with key improvements causing more problems than those they were designed to replace.

There’s no question the pedestrian path on the north side of Drake, between Eliseo Drive and El Portal, was a candidate for improvement. Overgrown brush often intruded into the path and guardrail was too short to provide a sense that it was effective protection.

County traffic safety experts should have seen that the replacement fence wasn’t any better from the standpoint of protecting pedestrians.

Fixing mistakes is one thing, but working to make sure they are not repeated is just as important. Supervisors need to take stock of the decision-making process that led to the designs of the lighting and fencing that now have to be redone.

What changes need to be made to help make sure similar mistakes aren’t made in future projects?

Taxpayers’ dollars deserve better.

Given Greenbrae neighbors’ history of being sensitive about lighting, the complaints generated by the new lighting likely were predictable. Was the fencing deemed to provide pedestrians adequate protection?

County officials have been responsive to complaints, but it would have been a lot cheaper and with much less consternation if after spending $18 million no follow-up mistakes needed to be fixed.