It isn't possible to force engineers to always walk all the way round, but I have been able to have a stable loop of about 300 tiles with just two engineers at the end points. The loop almost closes on itself, to force priests and librarians to walk around.
Sometimes engineers make very long walks, of about 200 tiles. I did observe that in a city consisting of just a single road of 3000 tiles. It appears that if you bend the road back on itself, the engineer will walk further in the same direction towards his home building, rather than turning back to the exact spawning point. The road looks like this
Legend(The glyphs work, great utility!, The dotted road tiles indicate long road ... .) The librarian always walks round the whole loop on his return trip, both engineers take the long road once or twice out of four.
Not all engineers make the long walks, and those who do, do so only one or two times out of the four repeating walks. It did take some micromanagement to have the two engineers walk out of fase, but I have a stable layout of a city now based upon this concept which can house 122k+ people. It just needs a few more hours running to get everyone in, I'm now at 60k and the population increase is just 3-4k/year game time. I can send you the city when it's finished.
I observed the long walk also with tax collectors, actors, and gladiators. I haven't built any prefect, as I'm working in Northern climate. My question was, has anyone experience with this type of forced walk.
[This message has been edited by joshofet (edited 06-17-2002 @ 06:11 AM).]