drivers license?

No, unless you need to drive to and from the airport. Your drivers license is only of value if you are driving in Europe. Some like to bring it along, some places want an ID to hold while using a audio tour device or similar "security deposit", but I have not really run into that. Your passport will work for that as well, but some people get weird about handing over their passport, somebody might steal state secrets or something. Aside from that, it really is not recognized as an "official" ID.

I bring mine along and keep it in my moneybelt. You never know when plans might change and renting a car may be an option.

Unless I need it my passport stays back in the hotel. I’m much less likely to lose it that way. I’d rather not spend valuable vacation time replacing it. I’ve used my DL for renting audio guides and for the rare occasion when I forget my keycard in my hotel room. And then there’s the issue of remembering to put it back into my wallet when I return.

I always prefer to bring my driver's license along with an International Driver's Permt, just in case I have to rent a car at some point during the trip. As others have mentioned, a D.L. is also good as a secondary form of I.D. which is useful for renting audio guides and things like that. There's no way I would ever leave my Passport for something like that.

In the rare situation where you have to sign a credit card slip, driver's license can sometimes be used. Also when using prebooked ticket to a museum. I used mine several times in England. Of course, it is my understanding that some countries, like Italy, require you to have your passport with you at all times.

If I carry my passport, it's in a secure place that's difficult to get to. I dread losing it because of the numerous hassles (been there, it's not fun) and then the expense of replacing it. A DL in my pocket is easy to show and it's almost always accepted as photo ID or proof of age. If it gets lost or stolen, it's not a problem on a trip (unless of course I'm renting a car), and it's easy and inexpensive to replace back home.

I bring it on every trip now just in case I need to rent a car, not just overseas but due to flight issues. I luckily had it with me when I was stuck in Houston in 2008 due to a hurricane and subsequent flight cancellations. I was able to rent a car and had to hotel hop for a few days as there were no vacancies anywhere near the airport. Taxis would have been extremely inconvenient and expensive.

Better to have it and not need it than the other way around...

Yes, bring your drivers license. I understand you are going on a tour, but if you do some exploring on your own, I have found that some museums require an ID in exchange for the audio guide and there is no way I am leaving my passport so my drivers license is what I give. I also need my DL to drive to the airport and home. I do not carry my passport around, just a color copy, so my DL acts as a secondary ID in case I am unconscious somewhere, unlike my passport, it has my home address so the authorities can possibly reach someone at my house.

Dave, We’ve gotten an International Drivers License from AAA. It costs $15 and is good for a year. We usually get it even if we’re not going to be driving in Europe for situations when someone wants to hold our ID for audio guides and such. Any time I’ve been asked for photo ID in Europe my passport was adequate, so I left the state drivers license at home during our recent trip last month so I didn’t risk losing it during my trip. Ellen

I'm usually driving so DL and IDP are regularly part of my travel kit. If you are sure you have no reason to drive, you might want it as a form of ID you can leave behind when asked. An example is getting the audio guide at a museum. They'll normally ask for some piece of ID that you get back when you return the headphones. Other examples are similar, they want something you aren't likely to leave behind.

Imagine your flight home is cancelled and you can immediately get a flight into an airport a 2 hour drive from your home. Would you take it and rent a car to drive home, or wait for a flight to your home airport? If driving is even remotely an option, bring your DL.