Renault mobility brand's first model promises to rewrite the city car rulebook in a fun-sized package Before we consider the weird - and perhaps wonderful - world of the Mobilize Duo, we should briefly revisit the car it ultimately succeeds: the Renault Twizy.There was plenty about that two-seater quadricycle that made it an illogical purchase. It didn't have windows or a heater, its electric range was less than 50 miles and it cost as much as most second-hand city cars of the period. But that didn't stop us from liking its charming, loveable character.Developed and built by Renault's urban mobility brand Mobilize, the new Duo looks set to continue that trend by taking the Twizy's fundamental principles and bringing them up to the standards of the day. It also promises to solve many of its inherent flaws with big-car equipment levels, a 100% increase in electric range, a design overhaul and - helpfully - windows.It has to, because even at this end of the car market - the 'sub-A' segment - there is competition from the likes of the Citroen Ami, the Micro Microlino, and the Luvly 0.Each of these future-gazing brands - particularly Mobilize - claim their machines will be practical, eco-friendly solutions to otherwise crowded transport in burgeoning cities over the next few years, but what's the Duo like in the here and now?The Mobilize Duo range at a glanceTwo versions of the Duo are available, each homologated to meet L6e and L7e quadricycle regulations depending on their weight, power output and top speed. The L6e variant, called Duo 80 Evo, has a top speed of 28mph and 8bhp, but it is not coming to the UK. The L7e variant - Duo 80 Pro - is coming here, and can be boosted up to 21bhp, with a top speed of 50mph.Directly beneath the driver's seat of both versions is a 10.3kWh nickel-manganese cobalt battery pack, which shuffles current, via a power inverter, to a rear-mounted electric motor. The battery yields a range of up to 100 miles on the WMTC (World Motorcycle Test Cycle) regimen used for quadricycles. In winter conditions, however, Renault said this should translate to around 62 miles.Those looking for more storage space, such as delivery drivers, can have the Bento, which trades the Duo's single rear seat for a load bay with a 649 litre-capacity. It's available only in L7e guise with its range slightly reduced from the Duo's, at 93 miles.The main focus of this review will be the Duo 80 Pro.