Getting access to a car in a city isn't always easy or affordable. Car sharing services are now launching that allow for short-term car use, without costing an arm and a leg. BMW offers its Drive Now service in London and worldwide.

We signed up to Drive Now and took to the streets of London in the BMW i3 to see what this offering is all about. How does it compare to Ford Go!Drive and is it better than traditional car rental offerings?

The thing about the BMW Drive Now service that makes it so convenient to use is its ease. Once you've setup an account, with driver's licence and insurance checks, all you do is tap your membership card on a car window and go.

Each of the cars, which include BMW 1 Series, Mini Countryman and the all electric BWM i3, are equipped with a window sensor. This wirelessly recognises if you registered and unlocks the car for use.

The service initially costs £29 to register then it's a flat 39p per minute charge when using the cars. Parking the car costs 19p per minute. Entering the congestion charge zone between 7am and 6pm on Monday to Friday will cost you the full £11.50 - something Ford's Go!Drive service offers for free. Drive Now also offers packages that drive the price down as low as 32p per minute.

To find a car near you there is a dedicated Drive Now app. This features a map that shows your location and all the nearest available cars. Tap an icon, and the car type along with a few details is displayed. We wanted to drive a BMW i3 from Shoreditch to King's Cross and had to only walk 7 minutes to the nearest car.

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After tapping Reserve, a 15-minute countdown begins. We got there with time to spare having seen the walk time shown on the map. There is an option to extend a reservation but this costs 19p per minute extra - the same charge as leaving the car parked.

In the app there is an option to select only the cars you want so if you're feeling picky. With 30 BMW i3s and 240 of the petrol cars there's plenty on offer.

We say we wanted to drive to King's Cross, in reality we'd like to have gone further west but in its current form the service is limited to northeast London, so you have to return the car to north London for final parking. You could drive it to Oxford and back (for example) but you'd be charged for the entire time, paying the parking rate when not in use outside the area of operation.

Driving any car in central London takes a fair bit of bravery. Stepping into a totally new car is a little frightening but once you're rolling it all comes naturally. These are really clean, modern and well kitted cars after all. Plus there are no fuel charges so finding a petrol station isn't a worry.

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The BMW i3 we were in featured a satnav system so after inputting our destination we were able to shut off and just enjoy the drive. The car had over 45 per cent charge so we didn't need to worry about stopping off or even plugging it in when we arrived.

Parking can be an issue. At the moment with Drive Now you have to aim at an area and hope there are parking spaces. In London this isn't always the case. In our experience we spent more time driving around one-way streets in King's Cross to find a space than we did driving there, in traffic, from Shoreditch. 

This is where services like Ford Go!Drive could be better thanks to dedicated parking bays. Although when there are spaces you might be able to park nearer your destination using Drive Now, it's down to luck really.

You are able to park on single yellow lines, pay and display spaces and even resident permit spots - apparently much to the chagrin of the locals.

The BMW Drive Now service frees you of owning a car. There are no insurance or monthy fees, not even petrol costs to worry about. Parking in London is made relatively easy by offering free parking pretty much anywhere you can park a car.

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The cars themselves are in great condition with satnav to help get your about town and aircon for a cool escape from the Underground in the summer.

The Drive Now service enables people to use cars casually, at the last minute, without committing to rentals for days or even leases for years. We're all for that.

Ultimately if these services catch on there should be fewer cars on the road and less money to pay for one, ideal for those who live in cities but need wheels for a trip to Ikea occasionally.

Compared to Ford Go!Drive, the BMW Drive Now service is more expensive and limited to a smaller area, but you can park anywhere. The service is still relatively new so we're excited about where it can go.

To use the service yourself you simply need a driver's licence and a smartphone. Give it a try and see what you think.

READ: Ford Go!Drive car sharing: Super affordable motor equivalent of 'Boris bikes' (hands-on)