Small Electric Vehicles—Benefits and Drawbacks for Sustainable Urban Development

The switch from ICE vehicles to electrically propelled vehicles itself holds many benefits especially in urban areas. SEVs and BEV have a positive effect on global climate and air quality. Charging of batteries using electricity generated on renewable energies increases the positive effects and does not simply shift the CO₂ tax geographically from the city to energy production plants based on fossil fuels [13]. However, low energy consumption is still important to mitigate negative impact from renewable energy generation and due to limited available energy amount.

Contradicting climate change mitigation efforts, a trend toward larger and heavier cars can be seen since the introduction of the first serial production EVs, as the technology is advancing in terms of, e.g., higher ranges. As a negative effect, this in turn requires larger and heavier batteries using more critical raw materials for the production of the batteries and making the cars inefficient in operation. Comparing an M1 electric car, the BMW i3, with an L7e category vehicle, the Renault Twizy, the BMW i3 has a significantly higher power consumption with 13.1 kWh/100 km (measured according to VO (EU) 715/2007 [14]) than the Twizy with 8.4 kWh/100 km [15] (ADAC-Autotest). Though the consumption statements are not directly comparable due to different test cycles and should therefore not be used to quantify relative energy savings, they show the energy inefficiency of heavy vehicles bearing in mind average occupancy rates of below two persons per vehicle [16]. The inefficiency can further be illustrated by comparing the range per kWh. In this way, an SEV with one kWh can go considerably further than an electric car. Figure 3 shows the relation between the Twizy with maximum speed of 45 and 80 km/h, a Smart for two and a Mercedes-Benz B-Class EV. Adding to this, the relation between transport task and vehicle weight is highly inefficient for passenger cars based on average occupation rate. The transport task passenger transport in Germany in average means a carrying capacity of 115 kg, calculated from the average occupation rate 1.5 [16] and the average weight of an adult person 77 kg [17]. While the weight of the Twizy exceeds this transport weight 4.3 times, the B-Class exceeds the average transport task by almost 14 times.

Increasing population in cities intensifies the situation of scarce space and raises the question of equitable contribution of land. The current land used for transport infrastructure accounts for a large part of the total area. For example, in German large cities, transport infrastructure takes up 12% in average of the total area and even a quarter of land used for transport infrastructure compared to human settlement areas [18]. Considering the average rate of occupation, private cars are the most intense mode of mobility occupying valuable space in cities [13].

Smaller sized vehicles take up less space on the road and require smaller parking spaces. An average parking space size of 5 m in length and approximately 2.5 m in width could be used by, e.g., three Renault Twizys or Toyota i-Roads.

Comparing space needed by SEVs, smaller M1 models, and large M1 cars, differences become apparent in parking position and in case of operation with speeds of 30 km/h (see Fig. 4). Taking into account stopping and reaction distance, the Renault Twizy needs about 20 m² less space than the Mercedes B-Class car in situations with 30 km/h speed. Differences in space requirement for driving are therefore minor compared to parking space potentials. Furthermore, the Mercedes B-Class enables the transport of up to five persons, resulting in a low space per person, However, with regard to average occupancy rates of 1.5 [16], this is a rather theoretical potential, used in a low percentage of trips. Even more, the figure shows the high potential for savings in land use for SEVs in parked position.

Although efforts are being made in some cities to introduce stricter regulations, e.g., in connection with the construction of new buildings, the cost of parking is mostly carried by residents. Less and smaller parking lots could decrease the overall costs for residents as well as for municipalities. Furthermore, under current circumstances SEVs spend less energy idling as they account for shorter parking search traffic than cars, because they fit in many different sized and shaped parking lots and usually can park crossways [7].

With regard to the actual potential for rededicating land used by cars, it is important to identify which user groups can switch to SEVs according to their travel behavior and how high the potential is. In the chapter “Fields of applications and transport-related potentials of small electric vehicles in Germany,” a technical feasible substitution potential is calculated using data from a national household survey (MiD).

Although the reduced size and weight bring many benefits for the user, municipalities, and the environment, they have a higher safety risk to occupants, especially in the event of a collision with larger vehicles. This is reflected by the results of the quantitative survey, where concern about more unsafe vehicles on the road is the second leading obstacle for SEVs in the opinion of the participants. In this case, occupants of the vehicle with the lowest mass sustain the highest damage [7]. Besides disadvantages for lightweight vehicles due to physical laws that determine accident dynamics of collisions with unequal opponents, safety features of both lightweight and heavy vehicles influence the extent of lesions in case of a collision.

On the one hand, SEVs are not equipped with extensive safety equipment due to the necessity of lightweight design and cost. In many countries and also according to EU regulations, crash tests for SEVs are not required by law. Therefore, the vehicles are equipped with minimal safety features [19]. Besides the lack of mandatory crash tests, there are safety requirements that are laid down in EU Regulation No. 168/2013 and the delegated EU Regulation No. 3/2014.

On the other hand, safety structures of heavy cars are not optimized for collisions with very lightweight vehicles and usually relatively rigid. Deformation of structures that would reduce impact forces by transforming kinetic energy into deformation energy is therefore limited. This cannot be compensated by structures of SEVs and thus leads to high deceleration of occupants in the lightweight vehicle, causing more severe injuries. High speeds of passenger cars add to the risks in case of an accident.

Extended safety features like airbags as standard equipment, improvement of vehicle structures and active safety features like emergency brake assistants could enhance safety of SEVs. Even more than technological measures, regulation could improve the situation for SEV occupants. When both SEVs and fast, heavy cars are mixed in high speed traffic, the safety risk is higher. The reduction of the maximum speed allowed, e.g., in inner-urban areas or city highways, would improve the situation. This would not only protect SEV occupants, but also vulnerable road users like mopeds, bicycles, or pedestrians. Scientific investigations show a direct link between reduction in average speed and decrease in accident numbers and crash severity, e.g., [20‐23]. The extent of safety increase varies depending on initial speed and further parameters like infrastructure characteristics. For urban roads, speeding is one key factor in traffic accidents with impacts on both frequency of crashes and severity of injuries [24].

Safety issues of transport modes like bicycles and mopeds are more severe compared to SEVs; however, in contrast to SEVs, they are sold and used in large volumes. It is common consent that safety could be increased by optimized traffic regulation and infrastructural measures rather than with enhanced safety structures of these kinds of vehicles. This is similar for SEVs, even though the safety potential of vehicle technology is considerably higher and should therefore be further developed additional to regulative and infrastructural measures.

The aspect of costs, in particular with regard to the purchase price, was discussed diversely in the qualitative analysis. In a comparison of costs, it is always very important to distinguish between the different types of vehicles. For example, the cost of owning or buying an SEV to offer in a sharing business is very high compared to e-scooters, bicycles, and some second-hand cars. Particularly in comparison with lower-priced cars, the purchase price can have a negative effect on the purchase decision, as SEVs often appear expensive with regard to limited flexibility in the transport of people and goods. However, compared to new cars, especially BEVs, they are relatively less expensive (Fig. 5).

For manufactures, the production costs for small series vehicles are significantly more expensive than mass production. However, in order to offer a vehicle to a broader user group, an attractive price is necessary. Manufacturers are therefore often faced with a dilemma. For example, by setting higher safety standards, they could offer a safer and high-quality product, but would have to set the selling price very high. For large companies developing a model for a small series vehicle in their portfolio often does not make sense as the economic risk is too high to invest in.

In the qualitative analysis, it became clear that the current situation is not favorable for SEVs in many countries, i.e., high speed limits in cities, no advantages in regards to parking or use of lanes, few incentives, few models on the market. In comparison with cars for many people, this leaves SEVs with few rewards to people considering them as relatively expensive.