Seven years ago Damian Harty, chief engineer, dynamics, at Prodrive, started thinking about a vehicle that would provide the agility of a motorbike but without the drawbacks of poor weather protection and vulnerability in the event of an accident. The resultant concept, referred to as the Naro car, was unveiled earlier in 2004 (Fig.1), but it is not the only narrow vehicle currently proposed as a solution to city traffic problems.

Urban congestion is a problem facing many European cities today, and there are also concerns about the environmental impact of personal transport. While public transport can help to alleviate congestion and pollution, it cannot resolve the problem of individuals wanting to travel to and from specific destinations at times that suit them.
A great deal of research has already been undertaken into the way in which narrow vehicles could benefit traffic flows in urban environments, and it has been shown that once a certain density is reached within the vehicle fleet, traffic queues can be shortened and journey times reduced. All of this is possible without making any changes to the infrastructure, and without narrow vehicles aggressively forcing their way between cars, lorries and busses.
In simple terms, once a certain proportion of the overall traffic is made up of narrow vehicles -- including motorbikes and scooters -- there is a greater probability that such vehicles will find themselves following each other in moving traffic. And when the traffic slows or stops, perhaps at traffic lights, those vehicles will naturally form-up abreast of each other instead of inline. For each pair, this has the effect of reducing the queue by one vehicle's length, hich helps to keep traffic flowing and reduce journey times.

There are limitations however, as visitors to cities such as Beijing will be aware; too many two-wheeled vehicles on a road network causes congestion in the same way as an excess of our-wheeled vehicles. So with Asia already well populated with narrow (two-wheeled) vehicles, and the USA having sufficient space that only a small number of cities suffer from severe traffic congestion, the main market for narrow vehicles is likely to be Europe. As Harty puts it: "In Europe we could make better use of the space e have with some narrow vehicles, and we are chaotic enough to allow people to make their own way through the infrastructure."
As the potential benefits are becoming apparent, something else interesting is happening: manufacturers are realising that there could be an entirely new market segment emerging. In the same way that the original Renault Espace created a new segment for vehicles larger than conventional cars, a new segment for sub-cars could be about to appear. Traditional brand hierarchies are lost in such a commercial environment, so manufacturers have everything to play for and are actively undertaking research and development (see panel). Harty says: "I never realised that I wanted to listen to my music collection whilst jogging -- until Sony told me I could by inventing the Walkman. Similarly, I think people will see narrow vehicles and suddenly realise that they no longer have to sit in traffic jams."
"I have always been passionate about motorcycles and reasonably evangelistic, but there are some people who will never ride a motorcycle because of the lack of weather protection and crash protection; so I wanted to find a way to ahave my cake and eat it'. Having spent a lot of time thinking about the technicalities and transport infrastructure problem, I concluded that we need to make better use of what we have got. In fact this is a Prodrive theme for vehicle development; we always make better use of what we have, rather than trying to invent a maglev (magnetic levitation) car or pushing for a motorsport rule change that would allow us to fit a jet engine."

Naro concepts

Working with Coventry University's Art and Design course, Prodrive has developed concepts of what its Naro car could look like using Harty's novel steering and leaning mechanism. Some illustrations show the vehicle as a single-passenger taxi (Fig.2), while others show it being used for pizza deliveries or personal transport. At 2.5m long it is the same length as a Smart car, but its weight of 300kg is less than half of that of a Smart car. With a small and efficient petrol or diesel engine the Naro car would be capable of up to 2.8litres/100km (100mpg), though the design leaves open the option for installing a new-generation fuel cell engine running on hydrogen. Something that is immediately apparent from the concept illustrations is how tall the vehicle is, especially in comparison with other narrow vehicles that have been proposed.
"The trouble with most narrow cars is that the engineers get hold of it," states Harty. "This results in a very low seating position to keep the centre of gravity low and make it easier to engineer. But nobody wants to be sitting low down in traffic."
The operative of a Naro car will have an eye-line at a height of about 1.5 to 1.6m, which is very similar to that on a sports motorcycle (the concept was based around the Honda Blackbird Harty owned at the time) and, surprisingly, the eye-line when standing upright. This compares with around 1.4m for a Ford Galaxy driver, 1.2m for a Ford Fiesta driver and 1.05m for a Porsche 911 driver.

Harty explains the need for a high seating position: "We need to give people some sort of offset, by saying: aYes, it is weird, buta' If we give them height, it gives back a feeling of control and perceived safety. This is the same as the way the height in an SUV [sports utility vehicle] gives a perception of safety, but if you abuse the steering wheel you can easily put it on its ear."
Making the Naro car tall and narrow (just slightly wider than the mirrors on Harty's Blackbird) will make it more difficult to engineer, but Harty insists that the Naro must be designed from the customer's perspective and the engineering must be in support of that. He is also emphatic that there are no areas of major technical risk. "The concept is innovative but all of the technologies already exist in current production vehicles. It is very important that it does not rely on a amagic bullet' or some piece of technology we haven't quite finalised yet. Yes, some of the technology is at the leading edge; for example, it is effectively steer-by-wire, but this is the same concept as BMW's active-steer system."

Human factors

But there are some major challenges relating to human factors. "One of the biggest questions is how it will work for the person. The technicalities have already been taken care of by God or Isaac Newton, depending on your preferences, because it is effectively two bikes shackled together. But how are we going to enable people to jump in and use it, despite it being very unfamiliar? We need to make it intuitive, but what exactly is intuitive? Should it be intuitive for a bike rider or for a car driver? A child learning to ride a bicycle will keep falling off because to balance it you need to steer the wrong way. Eventually, in desperation, the child does this and that then becomes instinctive. For me, as a bike rider, the abackwards' thing is very deeply ingrained, which is why I find it so hard to ride a wet bike or jet ski which work the opposite way. Because of this, I am adamant that the Naro car should not have handlebars.
"But I honestly don't know what it should have instead. A steering wheel, or a yoke, like a plane? The Vandenbrink Carver three-wheeler almost behaves like a plane -- but not quite. At low speed the steering input is treated as a yaw demand, but at high speed it is treated as a bank demand, with the software handling the changeover. In a plane, if you want to turn, you input a roll-acceleration demand; you have to put the stick back in the middle to hold the turn. Is that what we want?
We could put a load of people in a simulator and see what they do. Then we would choose what the majority do, but that would still leave a group of people who would be foxed by it. No, I don't yet know what the answer is."
Different variants of the Naro car are envisaged for different market sectors -- such as courier/delivery vehicles, taxis and personal transport -- and another of Harty's ideas could also be utilised here. Brand-by-wire is a concept whereby vehicle characteristics can be altered by changing the software that controls the way the vehicle behaves. For a vehicle that leans, whether a motorcycle or a narrow car, the way the vehicle rolls forms a large part of its character. Harty comments: "Some bikes are like small dogs that want to play all the time, while others feel longer and lazier." By adjusting the roll control system, the bulk of the Naro could be disguised to make it feel more lively, or it could be emphasised to give a greater feeling of reassurance."

Visual appeal

Despite his background as an engineer, Harty appreciates that the Naro car must be visually appealing in order to become acceptable. "Although it grieves me to say so, what it looks like is crucial. It must be something that is desirable, in an Apple iPod chic way, a cheeky MINI way or a funky Bauhaus AudiTT way. If it looks like a badly proportioned Reliant Robin, then people will think of it like that. But first of all we need to win over the journalists, remembering that technical superiority is no guarantee of success -- the classic case is VHS versus Betamax for video formats, where Betamax was far better quality but VHS somehow won over the market."

Theoretically a narrow vehicle only needs three wheels but Harty has insisted on four wheels to help gain public acceptance, despite this immediately incurring a 33 per cent wheel mass penalty. Having four wheels instead of three also has implications in terms of how the vehicle is viewed in the eyes of the law. In the UK vehicle taxation system there is a category of vehicles known as quadricycles that is taxed less heavily than cars. Currently the Naro car is too powerful to be classified as a quadricycle, so politicians are being lobbied to change the law to raise the maximum power of a quadricycle, with it being argued that such vehicles could help to solve the problem of urban congestion and pollution. Harty is not prepared to reduce the power of the vehicle as he insists that it must be able to perform well on any road -- including motorways -- as well as in towns and cities.
Prodrive has now licensed the Narrow Car Company to develop the project further and bring it to market (Fig. 3). Harty has no formal role in the new company but he says: "It's my baby and yes, I am heavily entwined with the project." Funding has already been secured for a prototyping phase and there is a bid in place for funding to take the project forwards towards production. Several bodies are said to be interested in the project, not all of them automotive manufacturers.
While the technical development of a tall, narrow vehicle that leans into corners is something can be taken care of by engineers like Harty by the end of the decade, the main challenges could be to make it usable and desirable enough by sufficient numbers of customers to make it commercially viable. Logically, it should be a success, but logic does not come with guarantees.