Now have rulebook to hand ...
No we specifically avoid Impact phases against anything already broken. It simply routs away and gets pursued. See age 100. All resolved in the JAP.
Under Initial Rout - p100 - it says they avoid obstructions as would evaders as it does on p108 for routs in the JAP; perhaps that is what you recall?
Otherwise I assume it is covered by p107 in the section on broken troops with enemy in contact at the start of the phase - which says they move directly away from the enemy in contact.
Yes Nik that's the section

and as it only says they
avoid obstructions by evade mechanisms they would indeed just wheel to get directly onto the line of rout and go as far as they can. One important thing there is that there is no choice about how they move, they are by this stage a law unto themselves.
I will pop this on across to the authors forum as well. Troops have to turn as part of an initial rout, even though it doesn't explictly say you can do so in the rules (unless I am missing something we put in). So how do troops who start their rout fighting and facing the enemy make their rout move if you can only wheel as part of a rout move?
Personally my intent for situations such as the one raised (i.e. where there is a direction change) was that the evade mechanism whould be used to find the shortest way to get onto the path of rout; its quite an elegant option to mix turns and wheels to get as far as possible. We use it for evade direction changes. We also put it in on page 100 when changing direction to move towards the base edge while routing (2nd bullet up on right hand side). The standard rout moves have sort of assumed you are lined up with enemy facing them as the normal situation, and not stated what happens to get you away.
Here is an example of why I think we need the turn/wheel combination. Imagine a line of 4 Cv routing. Now charge them from the
front with some of your troopsin the middle. How do they move? If they can only wheel, they have to wheel 178 degrees, say. But they can't as the new enemy are in the way. I suspect most of us would turn them 180 to run away, and then wheel them onto the line. But do the rules actually currently allow that? Otherwise they are simply destroyed as unable to complete a rout move (assuming you make sur the new contact is beyond the ability of the evade mechanisms to solve it). I would prefer our evade mechanism to turn them around and move them away.
So to surmise ... as written literallyat preset I think you would wheel in the situation raised ... but I am of the opinion that the evade direction change mechanism is a better method where direction changes are needed. More anon after discussing with Terry and Richard. Stick to the as worded version for now I would suggest.
Si