I believe the Dutch police is on record (somewhere) that they're glad when cyclists have lights at all and won't write you a ticket if you have a flashing light. Technically you need (orange) reflectors on your pedals and reflectors in your wheels as well. I have never been stopped for using "illegal" lights or lacking these reflectors; and you can always act the "dumb foreigner" and get them to sympathise by telling you came all the way to the Netherlands to ride a bike for 200km
Yeah, if the Dutch police enforced the rules then they would solve any budget issues in one evening of stopping people in Vondelpark...
My bike has all the reflectors needed by law, as well as a vast array of blinky, flashy, and steady lights (including attached to my body). I'll of course switch all bar 1 off on an Audax.
A helmet is not required by law, nor by the organisation of the brevets; but most Dutch randonneurs wear one.
I wear a Helmet to cycle even in Amsterdam, I just can't get used to not wearing one...
It's always windy over here, so keep wind chill in mind! You'll suffer without proper gloves (I like the "lobster" type, using it with a thin merino liner) and shoes with covers; MTB SPD cleats act like heat sinks, thicker insoles and/or heat packs (that are more like luke-warm than hot, for at most 3 hours IME) may be worth looking into.
Aye, I've got quite a nice collection of gloves for keeping my hands warm in various temps. I need to work on some nice overshoes tho.
I would recommend "warme chocolademelk met slagroom" to warm up at the controls
Lekker.
That bit I've got the hang of...
J