My wife and I will be in the Ypres area in July. We would like to walk a little of my grandfathers WW1 route. I was looking at starting probably around the area known as Polygon Wood and walking east as far as Keiberg and then circling back. Have a couple of questions.
The road I was looking at on Google Earth, Spilstraat, looks very narrow with no shoulders and I'm wondering if walking it might be a bad idea?
Secondly I don't see any public parking and was wondering if parking along the side of a roadway is OK or not. I could park maybe somewhere near the Polygon Wood or in the town of Molenaarelst.
Finally I note that on Google earth there are bus stops shown along roads in the area and I thought we could extend the length of our walk if we could get a bus back rather than walk. Has anyone used the bus system in that area who could explain how it works?

I too have visited WW1 sites in and around Ypres, but so far not Polygon Wood.
When I look at the areial view on the maps it appears there is now something resembling a large car park at Lange Dreve when it turns into Citernestraat. https://goo.gl/maps/61D6ybWJyHk The street view at this point is old (dated 2009) it is hard to confirm if it is a car park or hard standing the farmers use for storing and transferring crops. The website for the Cemetery unfortunately does not give any details on parking.
I expect you will find somewhere to park the car. Obviously just be ware of not blocking a farmers track/field entrance.
Walking should be ok. Being a Brit when walking in the road I still follow the highway code of facing the oncoming traffic. I am not a where of any such advice like that in the rest of Europe.
I cannot find Keiberg near to Polygon Wood. I found one some 150 plus kms away. SO I doubt if that is the location you wish to walk too.
Hope that helps in some way.

thankyou . Yes just did a search and a website for Zonnebeke mentions a new parking lot for Polygon Wood at that location. That would be perfect. I felt a little nervous of leaving a rental car parked on the side of the highway. The Keilberg I'm referring to is a small hamlet a little over 3 kilometers north east of the Polygon Wood. There are probably less than a dozen houses there.

I travel from The Netherlands back to Spain, The car is often loaded with luggage and "goodies" Never had any problems, Some WW1 sites are little way off the road with no parking near by. I have never had a problem. But I am just one person.
Have a great trip. Thankfully I do not have to do anything like this all of my family who fought thankfully came home. But I do not know any stories either about where they were stationed either.

Maybe these websites can be useful to you
http://www.wandelroutes.org/walking/polygon-wood
https://www.flandersfields.be/en/do/walks-and-around-zonnebeke
These are longer walks but if, for instance, you start at Tyne Cot Cemetery, it's only 4.5 kms to Polygon Wood.
If you have specific questions, send a mail to the tourist office. I know from experience that they are very helpful.

Yes, do be careful walking on the small roads-we noticed in Normandy that on the small roads (which of course have no sidewalks), the folks who live around there locally just come flying down the roads at top speed!

High speeds, that is the some all over the world. Or the world I have visited.

The Polygon Wood walk may fit. I can't seem to find the actual route on the website so I may have to get from the tourist office. The route of my grandfather's company attack was Polygon Wood towards Keilberg ridge where there was a fairly major battle. I wanted to follow in his footsteps up to that ridge. There is a route with what looks like a bicycle lane so that may be the best for us. One little problem...toilet facilities look sparse and there is nothing obvious in little hamlet of Keilberg. That will factor into the length of our walk.

I don't know that part of France well at all, but the speed limits on N roads in France are due to be reduced from 90kph to 80kph as of July 1, 2018 all over the country, so that should help a bit. We often encounter hikers on the rural D roads around here, and frankly, it's scary, even though we are local and drive slowly on these roads. Yes, walk facing the traffic, don't wear headphones (a lot of people do and it's insane!). Locals do fly on these roads! Friday is usually a sort of safe day, as it's the day the gendarmes go out in force on the roads to catch speeders and possible DUI suspects, so it's a pretty safe day to walk on no-sidewalk roads.

Ypres is not in France. Belgium 101. WW2 101.

France... the Belgiums may not be so pleased about that little change.
Besides a speed limit is posted does no mean that drivers adhere to that.