Ndtyjky

Sometimes when driving around town I'll encounter a small clog of slow-moving traffic driving slower than the speed limit, where I simply can't pass them. There's no traffic jam, accident, road construction, funeral procession, ulterior motives, etc, they're simply a random convergence of Sunday drivers. The only thing to do is wait until one of them turns.

I'm looking for a noun to describe the frustrating situation of being stuck behind them. It should work in the sentence "Well this is going to be a(n) ____________". Please don't suggest anything profane or indecent.

So far I've come up with "long haul", but I'm not sure the connotations are right, and I'm hoping for something that reveals more frustration than that.

EDIT: I'm looking for something that indicates both slowness and frustration and not just frustration alone, my mistake for not being more clear. Even better if it's somehow driving/transportation/movement related.

At your request, I propose:

Slow boat [to China]

On a slow boat to China

On a course or trajectory that will take a very long amount of time, especially with the conclusion or destination being uncertain.

from The Free Dictionary

I've put the "in China" in brackets, suggesting you drop it, because that element pertains to the second (unbolded) part of the definition above, i.e. that the destination is uncertain. This is also why the phrase is sometimes rendered "a slow boat to nowhere".

But in a car trip, your destination is certain. It's the amount of time you want to focus on, not the uncertainty of the destination, which doesn't apply in that scenario.

The phrase actually has an interesting history. We read in the same source:

A very long time. A poker players' expression for a player who constantly lost was “I'd like to get you on a slow boat to China,” meaning that the others would have all the time in the world to win the guy's money.

Composer Frank Loesser used the phrase as the title and the first line of a 1948 romantic ballad, and the expression started being used as a compliment.

The Wikipedia link about about the 1948 song describes a biography of Frank Loesser, its composer, written by his daughter. It pithily captures her conclusion about her father and his buddies’ coinage (or usage) of the phrase:

The idea being that a "slow boat to China" was the longest trip one could imagine.

a drag

A tedious experience, a bore, as in After several thousand times,
signing your autograph can be a drag. This seemingly modern term was
army slang during the Civil War. The allusion probably is to drag as
something that impedes progress. [Colloquial; mid-1800s]

This is going to be a pain.

This is going to be a bore.

This is going be a drag.

This is going to be a fag. !!
(Note: This only works in British English. In AmE it would probably be considered offensive because the word has a different meaning. See note below.)

NOTE

Fag

NOUN

British

1. informal in singular A tiring or unwelcome task.

‘it's too much of a fag to drive all the way there and back again’
https://en.oxforddictionaries.com/definition/fag

My first thought was at a snail's pace but that won't fit neatly in your example sentence (though it is relevant to the scenario). I couldn't find anything else closer in the mainstream dictionaries but thought you are caught in a snail race and got lucky with Urban Dictionary.

Well this is going to be a snail race.

Urban Dictionary:

snail race

When two semi trucks are taking up both lanes on a freeway and both
are going at least five miles under the speed limit but one is going
slightly faster than the other.

Passenger: Dude the speed limit is 70 why are you only going 60. 
Driver: Those two semi's are in a snail race, i can't get by them.

a bummer! TFD

1. an unpleasant or disappointing experience

As in:

"Well this is going to be a bummer".

Someone staying in a left lane at the same speed and distance as a car in the right lane, thus preventing you from passing, is sometimes called a formation flyer (no citation, but I've heard it), named after a flight formation of airplanes. Actually, the term can apply to cars in all lanes, if they make no attempt to enable those behind to pass.

So I'd coin the phrase formation-flyers frustration for the feeling you describe.