This little delivery robot, designed to autonomously navigate pavements, not roads, will this year begin making deliveries from businesses direct to customers.In doing so, it might just conquer e-commerce's final frontier: the Last Mile, the least efficient and most problematic step in the delivery process."Between 30% and 40% of the cost of delivery comes in the last mile," says Allan Martinson, the chief operating officer of Starship Technologies, the UK company building this robot.The little delivery robots designed by Starship are up against tech's strongest forces. Amazon is testing airborne drones, as are Walmart and Google. Google has also sought patents for a driverless truck that would carry an array of storage lockers that unlock with a text-message virtual key.Uber is deploying driverless cars for food delivery, a concept that could be expanded to other products.Although Starship's wheeled robot is the first to market, victory isn't assured. The droids have limitations - one is that their use is economical only in urban areas.Airborne drones cost more and have higher regulatory hurdles to surmount, but they might prove less expensive than droids on a per-kilometre basis.Because Starship's droids weigh less than 16kg and travel slowly, they are less likely to cause damage. They have no spinning rotor-blades that could cause injury - unlike drones.Most important, the droids travel on pavements not roads, which simplifies getting regulatory approval to operate. Starship robots have already covered more than 3057km in the UK, Germany, Belgium, Estonia and the US, with more than 80000km planned this year.In comparison, drone technology is being tested in highly controlled environments, and commercial deliveries are on hold until regulators work out safety, liability, air rights and privacy issues.Autonomous vehicles are so far allowed only limited tests on public roads."We've tested our droid in snow, slush, ice and rain - you name it," Starship's Martinson said.Gur Kimchi, the Amazon executive in charge of its Prime Air drone project, says Amazon has considered using delivery robots and driverless trucks but decided drones were a better bet."The other options cannot guarantee very fast, very economical and very safe delivery," he said. Drones, he said, can serve a range of rural, suburban and even urban environments - while delivery robots work well only in urban areas. And autonomous trucks or delivery drivers only add to the congestion on the roads.Kimchi said that Amazon's drones, which can carry up to 2.2kg for 24km at speeds of up to 96km/h, will cover 80% to 90% of its shipments."In a May 2015 analysis investment research firm ARK Invest estimated that by using drones Amazon could reduce its delivery costs to less than $1 per package.To ensure safety, drones have "sense and avoid" technology that will steer them clear of obstacles and hazards - including the family dog."If the drone cannot make the delivery safely it is programmed to abort and fly back home," Kimchi said.Without a clear regulatory framework, Amazon can't start using its drones commercially. So the company has proposed that a segment of airspace at between 60m and 120m be reserved for autonomous drones with sophisticated collision-avoidance and safety features, while lower-tech craft would be restricted to the airspace beneath 60m. Manned aircraft would stay above 150m.Kimchi said he thinks the regulatory framework will be in place "in much less than 10 years".Burton White, a consultant at Chainalytics, an Atlanta logistics consultancy, said retailers should wait for a shake-out. "This is still the Wild West," he said. "Drones are something to keep your eye on but they are further out."Starship thinks it will be able to lease its droids to shopkeepers w ith a target cost of $1.40 to $4.20 per delivery . This would allow small businesses that have been shut out of e-commerce by high delivery costs to begin selling online.The droids navigate using a 3G GPS signal. Nine cameras provide a fly's-eye view of its environment, and sensors help it avoid tree roots, toddlers and dog poo.Martinson estimates that the Starship robots have encountered during trials about 120000 pedestrians, including thousands of children. So far, no one has tried to abuse the robot."Children are curious but they love it," he said. ..