Half Marathon Twice = Marathon?

I would think it would be. There are many multi-loop marathon courses as well as lots of ultras (Lake Waramaug in CT comes to mind) that use multiples of a shorter certified loop to achieve a longer distance. Don't see why this would be different.
As to whether Boston etc. would accept the time as legit, that's another can of worms.

I'm thinking that Boston would require for this proposed double half-marathon to be run as a marathon race as opposed to this runner just continuing a half marathon race and doing the second loop by himself.

It would be the distance, but it would not be record eligible as there is no certification number.

The question has been asked here before about courses of other lengths, and I'm sure this one is no exception.

If the course was a loop course, integral multiples of it are considered certified, so the answer would be yes.

If the course starts and finishes at the same point, the start/finish point is considered a turnaround point for an event that would run over multiple laps of the course, so in that case the answer would also be yes.

In both of those cases, the drop and separation is zero, regardless of how many laps of the course you run.

In the example you cite, since the start and finish are not the same point, the drop and separation change depending on the number of laps of the course you run, so you would have to separately certify the marathon distance.

Jay, if the runner turned around at the Half finish, then ran the course in reverse, that should be a certified Marathon, correct? I am not comfortable saying it is a certified Marathon if they walk the 170 feet between the Half finish and the Start, as that is a rest (I am assuming they would stop the clock during the walk, otherwise they would run the 170 feet).

I agree that Boston likely won't accept it as a qualifier.

The marathon distance made by running this half marathon twice is surely correct as the half marathon is USATF certified. The drop and separation are record quality as the 170 feet are within the separation limit and there is 3-ft of drop. Walking the 170-ft is no different than stopping during a certified marathon and walking to a porta-potty. Running or walking the 170-ft has no bearing on the certified distance. I'm not sure why this runner wants to do this but if he were to try to use the double half as a Boston qualifier would the RRTC endorse it? There will be an official time (chip timed) for the double run.

Why not simply create another certificate for the full marathon? -- Justin

Duane, Appendix B of the measurement manual states "once the closed loop is certified, all integral multiples of the loop are automatically certified". We've apparently "extrapolated" that to equate an out and back course with a common start/finish point with a closed loop for this purpose. There's nothing that I can see in the manual that addresses running the course from start to finish and then turning around to run it from finish to start. We know the distance would be correct- but the rules in place don't provide for certification for the course at that distance.

I'm with Justin. If a runner wants to do this or something like it, the race organizer should have the course certified for the distance the runner wants to run. The measurement work is essentially done; you'd have to update the documentation.

Justin & Jay: I think you're advice is good but, in this case the course isn't a loop or an out and back. It can't be recertified as a full marathon without adjusting the start and finish. The race director and police want the finish where it is.

Again, would the RRTC endorse using 2consecutive fund of the half marathon course, with a 170-ft walk between them, as a Boston qualifier? I realize the RRTC does not make the final decision on Boston entries, but would this run-twice scheme be endorsed as meeting the marathon distance. This is all theoretical. I wouldn't expect Boston to consider the idea as a floodgate of this kind of multiple course runs would result
Lt.

Decades ago I organized a 50 mile race on a local bike path, and got it certified. The course was 2 ½ miles between two turn-around points, with the start/finish located at a handy place in mid-course.

It was advertised as the Wolfpack 50 miler. We expected and got fewer than 50 entrants.

Once the existence of the race became known, entries began to come in. Along with the 50 mile people we had a few who wanted to compete at other distances, notably 50 km, marathon, and 100 km. Grumbling, but trying to be Mr Nice Guy, I measured the extra bits and got them certified.

After seeing several examples of people wanting to run a race at a different distance than what is certified, I don’t think I would repeat accommodating special course changes to suit one or two people. Instead I’d politely refuse the request and advise the runner to seek out a race that is held on an already-certified course of the desired length.

Jay, you have a valid point regarding a closed-loop being specifically acceptable, but no mention of a point-to-point being reversed. This is a good example of making as few rules or definitions as possible, but then leaving similar scenarios open for debate later. For all who moan about new rules or definitions, this is one reason not to take a minimalist approach. (Soap box opportunity)

Guido Bros, with regard to the 170-foot porta-potty jaunt, it is different. In your example, the runner leaves and re-enters the course at the same location. In the scenario being discussed, the runner is exiting a measured course at one end, then re-entering the course at the opposite end.

I agree with Pete. If someone wants to run a marathon, they should to it on a certified marathon course. While a true closed-loop Half course would satisfy the "certified" criteria, it is up to the event to decide if they want to keep closures in-place, or course management and monitoring active for the duration of the second loop.

My opinion for the scenario being discussed is that it would not be considered a valid "timed" effort, as they completely left the measured course, and re-entered at a different spot on the course.