Emergency medical services (EMS) play a crucial role in healthcare systems. Their main goal is to reduce mortality and morbidity during emergencies. Within the scope of EMS is providing adequate prehospital care, including the transportation of patients, physicians or urgent supplies. Thereby, an important performance measure is the response time of calls (i.e. the period between an incoming emergency call and the arrival of medical staff at the scene). In recent years, it has become increasingly difficult for EMS systems to meet strict performance requirements, since demand has increased in many countries, due in part to ageing populations. Additionally, most EMS systems in developed countries encounter staff shortages. To maintain a high service level with limited resources, EMS systems must enhance productivity. Electric vertical take-off and landing (eVTOLs) vehicles are a recent innovation in aviation, offering a novel means of transport for EMS systems (Figure 1). Those aircraft share the vertical take-off and landing capability with conventional helicopters, while using a distributed electric powertrain system. This has various advantages in terms of operational costs, noise and sustainability when compared with helicopters. Hence, the implications may be significant for EMS systems.

Netherlands EMS transportation

An EMS provider in the north of the Netherlands researched the potential of eVTOLs to improve the performance of their existing EMS system. Most providers use ground ambulances and helicopters as primary modes of transport. Ground vehicles are flexible, inexpensive and widely used on land. However, their performance is highly dependent on road networks and traffic. Helicopters are operated under exceptional circumstances to reduce travel times in severe cases, or when the ground infrastructure does not allow vehicles. However, they are expensive to operate and cause high emissions in the form of noise and CO2 pollution. EMS in the Netherlands are operated by 25 regional ambulance services (RAVs). More than 800 ground ambulances are in service at 240 locations, with over 6,500 employees. The system provides a variety of healthcare transportation services between two main uses: urgent (A) and planned (B) transport of patients. Urgent transports are further divided into life-threatening (A1) and not life-threatening (A2). Dutch law stipulates that response times for A1 and A2 calls must not exceed 15 and 30 minutes, respectively, for 95 per cent of calls. In addition to the ground ambulance network, helicopters are stationed throughout the country. Four trauma helicopters are deployed in very severe cases, and one ambulance helicopter is used to transport patients from the Dutch islands to the mainland. The helicopter network operates in parallel to the ground ambulances – a hybrid system is not in operation.

Case study: Frisian Lakes

The Frisian Lakes area is a sparsely populated, rural region in the northwest of the Netherlands. The EMS system includes five evenly distributed ground stations. Four of these are equipped with one ambulance and one station (in Sneek) has two ambulances; the region becomes vulnerable when one vehicle is occupied, since the area around it can barely be covered by another station within 15 minutes. As shown on the right-hand-side of Figure 2, the region is characterized by numerous lakes and water channels that severely affect the road network and make some parts difficult to access. In recent years, the response time of emergency services in the Frisian Lakes area has been inadequate, at around 90 per cent. This is due to the difficult geography (bridges and few highways), while demand has increased and staffing levels are short.

Extension of EMS network

In terms of transportation, there are three different options that can address response performance in the Frisian Lake area. Firstly, increasing the number of ground vehicles that can be added to the network. This boosts availability, but utilization could be low, so it might not be cost efficient. Secondly, a helicopter can take over some emergency calls to decrease response times when it is exceeded by ground ambulances. On one hand, this helps performance, but helicopters are costly and cause high CO2 emissions and noise. The third option is to consider eVTOLs as an alternative method of transport in the system, as they are not dependent on road networks and expected to travel at speeds comparable with conventional helicopters.

An option is to consider eVTOLs as an alternative method of transport in the system

Therefore, eVTOLs can lead to shorter response times than ground vehicles, especially in such cases where ground units have lengthy travel times and, additionally, eVTOLs are expected to produce fewer pollutants, powered by an all-electric propulsion system – making the operation of these vehicles more convenient for communities. Nevertheless, eVTOLs currently have a decisive disadvantage compared with helicopters: the capacity of the current generation of eVTOLs is not able to transport patients. Instead, eVTOLs would benefit EMS systems by bringing medical staff to emergency locations faster, acting as doctor/paramedic shuttle. In cases where patient transportation is required, a ground vehicle would then have to be called for support. In this rapid responder role, more patients can be reached within the mandated target response time, increasing the EMS performance. The crucial 15-minute coverage area of an eVTOL is significantly larger than the one of ground ambulances, see Figure 3. This leads to the advantage that almost the entire Frisian Lakes area is covered twice. In this way, the eVTOL provides support to all ambulance stations when multiple incidents occur in the same area.

Simulation study

As eVTOLs have not yet entered the market, real-life experiments are not possible. Therefore, a simulation study was conducted to determine the value of an eVTOL in the current Frisian Lakes EMS system. The first step included building a simulation model of the current EMS network. It contains activities during the entire EMS process with corresponding time periods. Real-life input data of 2021 from the EMS system was used to validate the model. Secondly, an eVTOL station was added in the middle of the area with the following specifications, as outlined in Table 1.

Table 1. eVTOL specification in simulation model

With only ground ambulances currently, the closest available vehicle is dispatched to the emergency. To account for the possibility of sending different resources (ambulances or eVTOLs) to an incident, protocols had to be developed in the model: firstly, eVTOLs should be used when their expected response time is shorter than that of the nearest available vehicle; secondly, eVTOLs should only be dispatched if the expected response time of the closest available ambulance is higher than 12 minutes. In this way, the eVTOL is used only for long-distance missions, which leads to high availability and a decrease in lengthy response times. To test the system and find the parameters with the highest impact, experiments were conducted. Data from all 2021 missions was used to run the experiments. All listed eVTOL specifications, as well as the location of its station and different dispatching rules, were experimental variables. As an output parameter, the EMS performance level was measured: the percentage of emergencies that were served within a 15-minute response. The aim of the system was to reach a performance level of 95 per cent.

Simulation results – EMS performance with eVTOLs

To assess whether eVTOLs are of value for the EMS system in the Frisian Lakes area, the performance level of different set-ups was measured and compared. Figure 4 shows the current performance (data of 2021) and compares it with the situation with one additional ground ambulance (24hr shift), as well as the performance with an eVTOL (during daylight and in a 24hr shift). It is clear to see that eVTOLs provide a higher value than additional ground vehicles. However, the target performance of 95 per cent still cannot be reached with the used eVTOL specifications. The performance increase is mainly limited by eVTOL transport capacity, as the follow-up transport of patients to hospitals must be supported through ground ambulances.

When the average time for take-off or landing is reduced or the speed is increased, more emergencies can be served within 15 minutes

To identify the most influential parameters of the eVTOL operation, sensitivity analyses were conducted. Factors that directly relate to the response time of a call, such as the average cruise speed or the take-off and landing time, show high impact on the overall performance. When the average time for take-off or landing is reduced or the speed is increased, more emergencies can be served within 15 minutes, as the response time for eVTOL-operated calls decreases. On the other hand, poor weather conditions, charging times or the exact location of the eVTOL station have less impact on the network performance. These results depend on many assumptions and simplifications that had to be made to simulate the eVTOLs in EMS systems. For instance, eVTOL operation was assumed to be possible in terms of necessary infrastructure, regulations and personnel.

Future of eVTOLs in EMS

Hybrid systems with ground ambulances and air transportation via eVTOLs could help to overcome performance pressures on EMS systems.

eVTOLs can serve farther acute emergencies faster than ground ambulances

Especially in rural areas, eVTOLs can serve farther acute emergencies faster than ground ambulances, because they are not dependent on road infrastructure and can travel at high speeds. This leads to decreasing response times for the overall system. However, the performance increase is limited by the eVTOL transport capacity, as the follow-up transport of patients to hospitals must still be supported by the use of ground ambulances. Nevertheless, eVTOLs do show a higher performance increase when compared with additional ground units.