OK, so car2go can't make me do anything. But, will I end up driving more out of convenience since I've become a member? The short answer is probably not.
Since registering for car2go and receiving my keycard about a month ago, I have rented a car 4 times. I took one round trip and two one-way trips. The cost totals were $16.72 ($8.36 + $8.36), $7.22 and $7.60. The trips lasted between 19 and 22 minutes each. That's nearly $32 in just four weeks. Is that more than I would have spent on taxi cabs during the same period? Maybe. Unlike dealing with taxis though, I was able to reserve and access a car instantly, could not be passed up because a taxi was occupied --or for whatever other reason-- and was able to take the routes I knew to be the fastest and most efficient.
I compared the exact routes under normal traffic conditions using the Washington Post's taxi fare calculator. These estimates are under the new formula and rate structure for taximeters. The $7.22 car2go trip would have been $8.50 by taxi. The $16.72 round trip (really just two one way rentals) would have been $23.70. And the $7.60 trip would have been $11.25 by taxi. car2go total: $31.54. Estimated taxi total: $43.45. And that's without tip.
Two disclaimers: One, I rarely take cabs for trips like these. I almost always plan for and use public transportation or biking. And two, although I had the good fortune of finding car2go cars within two blocks my origin address, they aren't always available within such proximity. (There's an "unofficial/official" phone app which displays nearby cars and can also hold a car momentarily while you walk to unlock it. You can also just walk up to a car and swipe your card without "reserving.")
I consider car2go as an emergency back up to public transit that's not a cab. I have issues with taxi service in DC (another post, another time) and really try not to take a cab unless absolutely necessary. For example, when the H bus I needed pulled a no-show leaving me at risk of being late for a dinner in Glover Park, car2go came in handy. That car2go trip ($7.60) was spontaneous and I was able to catch the regularly scheduled buses for the return trip home. Could I have tried to flag down a taxi? Sure, but idly waiting for an empty taxi to pass though Mount Pleasant isn't always the best idea for a person late to a social engagement. I found a car2go car about a block and a half from the bus stop: problem solved.
Will I continue taking these trips for convenience sake? I'd like to think not. In a perfect world I like to minimize my dependence on cars and continue planning to take transit/bikes/walking to 99% of the places I regularly visit. Don't want to sweat in you suit on the way to a meeting? Next bus comes in 40 minutes? Procrastinated and late for that party? Those are all tough calls. Sure, I could hop in a car2go and remedy some of those issues. But in reality, I'd like to keep that option as a back up and save those $$$ for emergencies, social or otherwise.