I have a 1990 steel racing tandem, and sadly it gets more miles solo than with a stoker.
The main differences between tandems and solo bikes apply when riding a tandem on your own (rear wheel cuts corners more, you can't bunny hop) but points to note:
Cars may not see the rear of your bike, and may not anticipate the extra space required when pulling up or allowing room to turn.
Steering is a bit odd - it may be unique to mine, but if the solocaptain doesn't commit to a corner with enough lean, the bike tries to stand up straight and go straight.
Braking - its still possible to raise the back wheel clear off the ground when doing an aggressive brake with just a captain.
And the stoker's bars may get in the way of your backside if you lean backwards.
Drag brake is less effective with no stoker.
So big descents you have to ride more like a solo bike.
You may get heckled with "Your passenger fell off!"
so have a witty retort like "Bugger -
so that's why she stopped nagging!"
or "Damn I thought we were going slower than normal!"
Speed is generally not an issue - I've topped 40 km/h solo on my tandem, and the previous owner exceeded 70 km/h on it on a race, with two riders.
bicycles.stackexchange.com/users/19705/Criggie
Doesn't seem like too big a deal.
It should be similar to having someone on the back who's not pedaling, only lighter and faster.
bicycles.stackexchange.com/users/14375/BSO rider
I have a tandem
and I have ridden it solo.
It's not hard from a handling point of view, and at least with mine it's easier than riding tandem – it's just riding a bike with an exceptionally long rear end.
Sure, more friction and a lot more weight, but overall something any cyclist with a tiny amount of experience can handle.
bicycles.stackexchange.com/users/4601/chichak
Riding a tandem solo isn't a big deal.
It's just a big long heavy bike; as others have said easier than riding a tandem with a stoker if they're not putting much power in.
Apart from the "funny" comments you get, the only actual issue I've noticed is that you don't get so much grip on the back wheel without the weight over it.
I tried standing on the pedals going up a hill and found the wheel would spin.
bicycles.stackexchange.com/users/13824/Chris Emerson
It will certainly be more difficult than riding a standard bicycle.
Although I don't feel like it would be impossible by any means.
The factors to consider are: Weight -
the Tandem weighs a lot more than a standard bicycle Wind - larger surface area means more effect from crosswinds Length -
This will play very little with the transport as far as riding it to a friends house, other than turning, but plays a major factor in future transport by car or bus Tandems have a pilot, and a stoker, the rear rider being the stoker, and all steering is done by the pilot or front riding.
Therefor the stoker is only there to help out with pedaling and enjoy the ride.
So yes it will be more difficult but I wouldn't rule it entirely impossible.
You will look lonely however ;)
bicycles.stackexchange.com/users/24618/Nate W
It's usually easier than with a partner.
I've been on one home-welded tandem where the front and back pedal cogs had different number of teeth and thus were not synchronized.
That posed a problem for leaning into curves since the reflex of putting the inner pedal up did not match with the other pedal pair.
It's astonishing how much of a nuisance this can end up being (and when going solo, you had no warning).
I don't think that this happens with a stock tandem however.
bicycles.stackexchange.com/users/25032/user25032
About 4 miles away from me, there is a bike hire shop that has tandems. I'm trying to work out the logistics of getting the tandem to my house to pick up the other rider.  I'm an experienced cyclist, but have never ridden a tandem before. It's not convenient for both of us to go to the shop. Is riding a tandem particularly difficult for one person?  I suppose I'll get the bus there...
Is it difficult for one person to ride a tandem bike?
bicycles.stackexchange.com
<tandems>
bicycles.stackexchange.com/questions/37639
bicycles.stackexchange.com/users/19321/Ne Mo
Many cyclists appear to be of the opinion that, contrary to what you would believe, riding a tandem alone is often easier than riding with a partner. Things to look out for, however, include a heavier bike, a longer bike so needs to be taken into consideration when cornering and back wheel coming off the ground in an emergency stop,  It is certainly possible, but the longer rear and heavier weight will make it more difficult to ride and handle than a solo bike. Cars may not expect the extra length at the back, and the lack of a rear rider will affect traction and braking on the rear wheel. Normally the captain controls the steering and braking anyway, so handling may be easier than with a partner and the difficulty will depend on whether the partner is normally pulling their weight.
It is certainly possible, but the longer rear and heavier weight will make it more difficult to ride and handle than a solo bike. Cars may not expect the extra length at the back, and the lack of a rear rider will affect traction and braking on the rear wheel. Normally the captain controls the steering and braking anyway, so handling may be easier than with a partner and the difficulty will depend on whether the partner is normally pulling their weight.