PRE2016 3 Groep20
Group members
Lotte Aerssen - 0892039
Wouter van den Bemd - 0948482
Lennard Kerkhoven - 0955882
Bjorn Walk - 0964797
Wouter Weekers - 0956095
Noud Schoenmakers - 0938197
Introduction
The current delivery systems that are available in the Netherlands are failing to deliver. There are three reasons that show it has to be changed. First the delivery times are too long, people and small businesses rely to receive their packages as soon as possible. However, because of dense traffic and crowded streets the orders take too long. Also in the ever changing society of today people are not bound to one location anymore. The society is craving for a system that delivers their packages on-the-go. Finally the the companies only deliver in a given time frame, thus the costumer needs to stay home if he wants to receive the package. This even fails because of the systems that are used by the companies where emails and apps fail to deliver.
These reasons show that the delivery system is in need of innovation. This report will elaborate the options on how to do so. Then one of the options will be chosen after an elaborate research and carefully taking the user in consideration.
User needs
In the ever changing environment of today, the customer and small businesses rely on the postal service’s fast delivery traject. However the future will need a faster, more reliable and more user centered traject of postal delivery. Therefore we want to develop a system that brings postal packages faster to the customers and does this in a diverse way where it will even be possible to order AND receive packages on-the-go. Thus it will not only be faster and more reliable, it will bring the user(customer) back to the center again with a system that introduces a complete new approach to the world of postal service delivery.
Approach
One of the goals of our system is that it tackles problems with regard to urban and countryside delivery of packages. This could feature a two way system. For instance, when the package needs to go to an urban environment, it could be delivered using autonomous busses. The delivery to the countryside could be done using aerial vehicles such as drones, airplanes, balloons etc.
Therefore the project will focus and investigate multiple possibilities of postal delivery services and it will not just focus on, for example, drones because there are numerous possibilities regarding the approach of autonomous postal delivery services.
Further, it is important that there is a possibility to grow for this project. For example, when designing a system that could be used for urban environments. One of the solutions could be a massive tubing system. This could make the delivery of postal services fast. However the we want a system that is designed for the user and around the environment of the user. Thus the city should not be designed around the system, the system should be designed for the city. This is an important issue since one of the goals is to make a system that has the ability to grow. Therefore it is important that it is diverse and impliable in every environment so that it could be possible to grow from city scale to a world wide system.
Boundary conditions
Some important boundary conditions are:
- safety
- weather resistance
- speed
- diversity
- sustainability
Ideas
The creation of a system with 'on-the-go' availability a system with a portable landing site could be used. To reach the customer when he is at the camping for instance, a portable landing site could be used for instance, such as the image below.
Options
There are a few options on how to design such a system. First, the system could go over land or by air. Both bring an their own drawbacks but also their benefits to the problem.
Differences between rural and urban areas
Urban and country delivery systems need a different approach when it comes to autonomous package delivery. Urban zones are high populated areas which contain many buildings which can be tall. Urban zones are usually located in cities or towns and contain many roads. Country areas are very different to urban zones because they have a low population density with fewer but longer roads of which some may be unpaved. High buildings are less likely in country areas but trees are more common.
Delivery system for rural areas
Delivery systems in rural areas preferably have a high travel speed as great distances are common. High speed wheeled robots that travel on the road and flying robots meet these requirements. Flying robots are preferable since they do not need advanced hardware to deal with other traffic. Another downside of wheeled robots is that the technology to take place in traffic is also not fully developed. Flying robots can travel easily over the often low buildings and trees in rural areas with a very low chance of having a dangerous crash with a person.
Delivery system for urban areas
In urban areas, a way to travel is preferred where the complexity of the environment does not affect the robot too much. Safety is also an issue, since it is a highly populated area. Slow moving robots are preferred because this makes collisions less dangerous. Legged robots or wheeled robots which travel on the sidewalk are perfect for this environment. Low travel speeds do not matter since travel distances are usually small in urban areas. The sidewalk is a relatively simple environment, which makes movement easier. Flying robots and high speed wheeled robots are not safe enough because the complexity on the road or in the air between the tall buildings makes it likely to crash, which is rather dangerous for such high speed systems.
Options for delivery
There are many different methods to move from point A to point B. One obvious method is by using wheels. Robots on wheels are well developed but they require pavement to function reliably and they cannot handle stairs. Travel speeds of wheeled robots are usually slow if they travel on the sidewalk where high speed motorized vehicles are not allowed. Driving on the road allows higher speeds, but the robot has to be equipped with more advanced hardware, thus raising the price. Another way to move is by using propellers to fly, which can be very fast. Important disadvantages are that packages cannot be very heavy, tall buildings have to be avoided and a crash in a populated area can be dangerous. Finally legs can be used to move from one location to another. At the moment legs are one of the most challenging ways to move around as a robot, since balancing on different surfaces can be quite a challenge. This way of movement is similar to the robots on wheels. The main difference is that a robot with legs can walk stairs and is less likely to get stuck on unpaved roads.
Helicopter
The helicopter is an airborne vehicle which can carry a package. This particular option has a lot in common with the system used by Amazon Prime air. This small and lightweight vehicle type can only carry relatively light loads, as weight has a strong impact on battery life. It usually travels very fast at a certain altitude. In case of Amazon Prime Air this height will be 100 meters and the speed will be up to 80 km/h. The drone will carry the package in a safe, which can only be opened by the authorized person using his or her smartphone.
Effectivity
As helicopters are not affected by the quality or presence of roads they can be used in both urban and rural areas, making them very diverse and suited for all kind of environments. Package delivery requires a place to land, which renders it useless at locations without a proper landing spot. However, the spots do not have to be big, as the vehicle itself is small. The helicopter is also very effective at places with a bad infrastructure, because it can fly over obstacles. They also travel very fast and always travel the shortest route, which gives the fastest delivery time besides the plane compared to the other options. Maximum package size and weight is somewhat limited, since a helicopter has to constantly fight gravity and increasing the weight will increase the load. The range of a helicopter is also limited, as flying uses a lot of battery power and big battery packs can not be used due to weight.
Reliability
Helicopters are heavily dependent on the weather. Fast winds, pouring rain and snow all affect the helicopter. Of course there are modifications available to make a helicopter waterproof or increase the strength of the motor, but this also increases the weight and therefore decreases flight time and increases the power consumption of a helicopter.
Safety and privacy
Overall, the chance of a collision and a person or property, is very small for a helicopter. This is because it travels in the open air, with almost no obstacles to collide with. However, in the event of a crash, a helicopter will drop from a high altitude, which could be a very dangerous situation. This can be prevented by applying several backup systems in such a helicopter, so it can for example still fly with one or two malfunctioning motors. On the subject of privacy, the drone will need cameras and sensors to land at a certain position. This could violate privacy, however, if the images are automatically interpreted and deleted by the helicopter afterwards, it will not influence privacy at all.
Protection of the package
The fact that this option is airborne means that it has less risk of being damaged assuming there are traffic rules for drones. Its altitude ensures that the system can not be abused by a third party. The only moment where it is vulnerable is at the delivery point. Therefore it should not stay long at the delivery point, even though it has a protected safe.
Costs
The price of such a system is heavily dependent on the assumptions. Making a helicopter water resistant or adding more safety precautions may increase the price of the system.
Plane
A package delivering plane will generally travel very fast, as this is required to generate enough lift for the plane to carry the package. This vehicle can only carry lightweight packages, as weight has a strong impact on the battery life. This vehicle will travel at an altitude of about 100 meters, which is the same altitude as Amazon Prime Air. Typical speeds for radio controlled aircraft are between 120 and 180 km/h. Dropping the packages will require parachutes and a certain drop off location.
Effectivity
This option is definitely the option with the fastest delivery time. With the highest travel speed of all options and the fact that it can fly straight to the target, the plane will be able to deliver a package within minutes. The maximum package size is somewhat limited, as extra weight makes the flight time lower. The fact that it ignores waters, roads and other obstacles, makes the plane useful in areas that cannot always easily be reached.
Reliability
Planes are dependent on the weather. Fast winds, pouring rain and snow all affect the helicopter. Of course there are modifications available to make a plane waterproof or increase the strength of the motor, but this also increases the weight and therefore the flight time decreases and the power consumption increases.
Safety and privacy
Airborne vehicles have only small chances of collisions in air, which can be avoided with air traffic laws. One problem with planes is that they cannot stop flying when needed. Helicopters for example can slow down and then slowly decrease its altitude until it touches the ground. Planes need a runway to stop, which might become a problem above urban areas. Crashing of a plane can be severe due to the high speed and altitude at which it travels. Planes will also need multiple sensor to calculate how to drop off a package. This may offend privacy if the images are not immediately deleted.
Protection of the package
A plane will need to land on a landing strip if it wants to deliverDelivering a package will require dropping it from the plane,. Packages will have a parachute attached to it and they will be packed in protective wraps, which will ensure a safe landing for the package. A problem with this is that there is no good way to prevent unauthorized persons to grab the package, as the person cannot authenticate with his or her mobile phone while the plane is midair.
Costs
The costs of such a plane is heavily dependent, adding modifications can cost a lot of money but may increase reliability. One side effect of the plane is that protective packaging materials will be used, which will increase the costs per delivery.
Walking robot
This robot uses legs to move on the sidewalk from point A to point B. It uses sensors to avoid collisions with obstacles or persons and it can use GPS service to move itself towards the destination. This type of robot is very similar to the already built Cassie robot. Using legs instead of wheels allow the robot to walk on stairs and decreases the chance to get stuck on bumps on the sidewalk compared to wheels. The movement speed of the robot will be about the movement speed of an average pedestrian.
Effectivity
Delivering packages at the speed of an average pedestrian takes a very long time. Therefore the robot is only effective in a small range around the package disposal station. For covering large areas, a lot of disposal stations have to be placed and these also have to be supplied with goods. This is fine for small systems where only one disposal station is required, for example a pizza delivery service. The products will then be produced and disposed at the same location. This removes the struggle of filling the right disposal stations with the right products which makes the process much more slow because of the extra step in the transport process and therefore less effective. A system like this would only work well for small areas with a dense population. It can be concluded that the system will be effective in urban areas for local companies and less effective or even obsolete for greater delivery areas or a rural area with a low population density.
Reliability
Reliability is an important factor for a delivery system. Small delivery robots can be very reliable under the right conditions which leads to a trustworthy delivery system. Walking robots are unlikely to damage the package. This is because they move very slow and store the packages in a safe inside the robot, which in the uncommon event of a collision prevents damage to the package. In an event of hardware failure, the robot will also be rather safe, as the robot moves very slowly. The central station will be notified since the robot does not move. A repair mechanic can be send towards the robot to fix it, which causes a slight delay in delivery time but no damage to the package.
Safety and privacy
A walking robot only participates in a few ways in traffic. First of all it must be able to safely walk on the sidewalk using its sensors to avoid obstacles and humans or pets. A collision with a person will be very unlikely because distance sensors can check whether there is an object in from of them and then automatically stop moving. Therefore the only real threat is a human or vehicle which bumps into the robot, which can be more dangerous. Also, the robot must be able to cross a road, which is more complex than walking on the sidewalk, as it has to recognize whether it is safe to cross, taking different traffic into account and their different roles and speeds. This can become quite challenging but autonomous cars by Google have proven that autonomous driving is possible. This also includes an extensive monitoring system which can determine where every traffic participant around the vehicle is located and which speed it has.
Protection of the system and the package
A walking robot will be a very vulnerable robot, as it moves slowly and it is not that heavy due to its maximum size. The robot will need some sort of package protection safe which can be opened using NFC on the smartphone of the customer. To prevent stealing the vehicle as a whole, anti-theft features should be implemented. This can be done by using the tracker that is already in the robot, or by using a loud alarm which goes off once the robot is lifted up or damaged. This should also immediately send a warning message to the staff of the delivery system who can warn the police if it is necessary.
Costs
The costs of such a vehicle might be high, as it needs many sensors to observe its environment. Out of all these sensors the visual sensors are the most expensive as it needs both the cameras and computational power to process the images and locate all the obstacles. Also, the fact that many disposal stations will be required makes this system even more expensive.
Sidewalk Cart
This vehicle moves packages from point A to point B using the sidewalk. It has various sensors to avoid collisions with obstacles or persons and it is able to use GPS to move itself towards the destination using wheels. The packages these robots can carry can be quite heavy, however, the volume of a packet will be limited. This is because the robot has to be able to avoid obstacles on the sidewalk, which cannot be done if the dimensions of the cart including the package are too big. The movement speed of the robot will be about the movement speed of an average pedestrian.
Effectivity
A small delivery unit that travels at the speed of an average pedestrian which is about 5 kilometers an hour is very slow. This makes the robot only effective in a small range around the package disposal station. For covering large areas, a lot of disposal stations have to be placed and these disposal stations also have to be supplied with goods. This is fine for small systems where only one disposal station is required, for example a pizza delivery service. The products will then be produced and disposed at the same location. This removes the struggle of filling the right disposal stations with the right products which makes the process much more slow because of the extra step in the transport process and therefore less effective. A system like this would only work well for small areas with a dense population. There can be concluded that the system will be effective in urban areas for local companies and less effective or even obsolete for greater delivery areas or a rural area with a low population density.
Reliability
Reliability is an important factor for a delivery system. Small delivery robots can be very reliable under the right conditions which leads to a trustworthy delivery system. Sidewalk carts are very unlikely to damage the package. This is because it moves very slow and stores the packages in a safe inside the cart, which in the uncommon event of an collision prevents damage to the package. The robot however has a chance to get stuck by for example driving on uneven terrain. The robot will be able to notice that it is stuck and send a warning to the central station, where a human controller can try to unstuck the robot. In an event of hardware failure, the robot will also be rather safe, as the robot moves very slowly. The central station will be notified since the robot does not move. A repair mechanic can be send towards the robot to fix it, which causes a slight delay in delivery time but no damage to the package
Safety in traffic
A sidewalk cart only participates in a few ways in traffic. First of all it must be able to safely walk on the sidewalk using its sensors to avoid obstacles and humans or pets. A collision with a person will be very unlikely because distance sensors can check whether there is an object in from of them and then automatically stop moving. Therefore the only real threat is a human or vehicle which bumps into the cart, which can be more dangerous. Also, the robot must be able to cross a road, which is more complex than walking on the sidewalk, as it has to recognize whether it is safe to cross, taking different traffic into account and their different roles and speeds. This can become quite challenging but autonomous cars by Google have proven that autonomous driving is possible. This also includes an extensive monitoring system which can determine where every traffic participant around the vehicle is located and which speed it has. The question however is how much a sidewalk cart can monitor as it is such a small vehicle.
Protection of system and the package
Stealing packages, destroying the equipment or stealing the robot as a whole are all forms of abuse. A sidewalk cart will be a very vulnerable vehicle, as it moves slowly and it is not that heavy due to its maximum size. The robot will need some sort of package protection safe which can be opened using NFC on the smartphone of the customer. To prevent stealing the vehicle as a whole, anti-theft features should be implemented. This can be done by using the tracker that is already in the robot, or by using a loud alarm which goes off once the robot is lifted up or damaged. This should also immediately send a warning message to the staff of the delivery system who can warn the police if it is necessary.
Costs
The costs of such a vehicle might be high, as it needs many sensors to observe its environment. Out of all these sensors the visual sensor are the most expensive as it needs both the cameras and computational power to process the images and locate all the obstacles. Also, the fact that many disposal stations will be required makes this system even more expensive.
Road cart
This vehicle delivers packages by traveling over the normal roads cars use. Because of this the road carts are much like the delivery vans that are used today. However there are a few differences to make it an autonomous delivery system. Firstly it drives completely autonomous. To make this possible it has to have a lot of sensors, GPS and AI to make decisions. Secondly the unloading of the package is also done autonomously. Due to its large storage area the road cart can carry large and heavy items. The road cart can travel at the same speeds as normal delivery vans can.
Effectivity
As said before the road cart is basically like the vans used today. This makes them effective in a large range, because they can travel at high speeds. Also the large storage space the vans have makes it possible to take a lot of packages in one run. This however introduces another difficulty namely the one of taking the right package at the right location. However there are already systems that can do this, making the road cart an option for both rural and urban areas.
Reliability
To be reliable the delivery vehicle has to be able to deliver the package safely and on the scheduled time at its destination. Road carts travel by the roads between the normal traffic. This makes its arrival times uncertain as there are a lot of things that can delay the vehicle, such as traffic jams or crashes. Another problem is possible damage to the packages. Because the storage room of the vehicle is large there is a lot of room for the package to move around when taking turns or crashing if it is not tightened secure enough causing possible damage to it. Also, when having either a software or a hardware failure the autonomous cart can become a dangerous projectile as it can travel at high speeds making safety an issue.
Safety in traffic
The road cart participates in the busy traffic on the roads. Therefore it has to have sensors to prevent collision. This technology is already used by for example Tesla for the autopilot function, so this should not be a problem. The only problem is thus when another vehicle crashes into the cart, but this is a problem all vehicles on the road face so there is no reason this should be the reason not to choose this option compared to the vans used today.
Protection of the system and the package
A road cart will not be very vulnerable to abuse, because it will most likely be the size of a normal delivery vehicle so it cannot be picked up like for example the sidewalk cart. The road cart can also be locked automatically when no package is getting dropped off. So abuse of the road cart will not be a big problem.
Costs
The costs of the road cart might be very high as it needs a lot of technology to make sure the package gets delivered safely, but with the rapid growth of technology these techniques will get cheaper.
The zeppelin
One of the options is to make the system by using a zeppelin. It will take the packages from A to B through the air. It will use GPS to know its location and use some sort of engine to propel itself through the sky.
Effectivity
One of the options of a package delivery system is to take it to the sky and using a zeppelin to do so. While this option seems outdated it has some advantages that other technologies still not have overcome:
For instance, safety. When a zeppelin is struck by something and the gas flows out of the balloon, it drifts towards the ground on a slow manner. In comparison with a heavy helicopter or plane this is a great advantage.
Next, the lift force. A zeppelin can easily be adjusted to have a high lift force. The addition of light gasses make it possible to take heavy objects to the sky. This is a big difference with other aerial options.
Also the power consummation is much lower on a zeppelin, the balloon requires no to low additional energy, the balloon floats around. The only consummation of power is the way it propels itself through the sky using, for instance, propellers.
Reliability
One of the big drawbacks of a balloon based system is the speed of it. These means of transportation are not known for their speed. On the contrary, it is a very slow. Also since it is so big it is an object that can be easily hit by other objects and even damage wildlife when birds fly into it. Also the low weight of the zeppelin makes it very sensitive for winds and other weather influences.
Safety in traffic
As described in the Effectivity, one of the advantages of the Zepplin is the safety. The balloon will never fall as a brick from the sky due to the slow gas flow out of the balloon. This gives the citizens more time to get clear of the falling object. Also won't the impact be high due to the slow speed of the falling object. However, due to it's size it is big enough to be hit by something and what happens when the zepplin crash lands on the high way. This could lead to crash of traffic due to it's size.
Protection of the system and the package
The zepplin is a system that could be easily abused. Simple teenagers with a blow dart could even be the reason the zeppelin could crash. This one of the problems with the development of the system because the material should not be easily penetrable but still lightweight. Then, when the zeppelin has crashed the safety of the package has the same problems as all of the devices: how to keep them locked up. Here the zeppelin is in the advantage because of its lift force, a safe could be mounted under the device making it less easy to break open. Also the size of the object makes it hard to be taken away.
Costs
Since there is no company that has ever produced a prototype where a balloon technology is used to deliver packages it is hard to determine the costs. One way to estimate it is using the costs of blimps and scale them by lift force and then do so by the price as well. The Skyship 600[3] for example could lift roughly 2300 kg. Since the aimed packages are 2 kg the blimp can be scaled down by 1000. This gives a device with 6 m^3 of gas, thus roughly it would be 3x2x1 m. The costs of the blimp whould therefor be around $15.000,-. Since the original costs $15.000.000,-[4]. Still since this smaller blimp would ask for less expensive engines it could come cheaper. Also the Airship 600 features a cabin for crew and passengers. Still it is an estimation for the costs to develop such device.
The choice
The current situation
Rules and Regulation drones (Netherlands)
There are no clear rules for autonomous drones stated in the legislation of the Netherlands, therefore the rules for professional use will be used as rules for the autonomous drones. In the legislation drones are divided in light drones which weight up until max 4 kilogram takeoff weight, and heavy drones which weight up until 250 kilogram takeoff weight. For packaging drones the focus will be on the light drones. The drone always need to give priority to all other air- and land-traffic when they are approaching. They also need to fly in daylight and may not fly in the dark. The drones may not fly higher than 120 meter and need to have a minimum distance from crowds, compact building density, artworks, harbors, industrial areas, railways, public roads, vessels and vehicles of 50 meters. There are also No-Fly-Zones in the Netherlands were no drones are allowed to fly. As you can see are the No-Fly-Zones mainly in big cities and airports. The red area's are the the No-Fly-Zones for the drones.
source: www.rijksoverheid.nl
The package delivery
The package delivery system can be separated in several steps. One of the biggest delivery companies in the Netherlands is PostNL. A description of a possible package order process looks like this.
1. When a client orders a product from a web shop the web shop sends the product, from its own stockroom, in a package to a sorting center of a delivery company.
2. In the sorting center all the packages that need to be delivered in a certain region in the country are gathered.
3. When there are enough packages to fill a vehicle (van or truck) the packages are transported to the right region and delivered to a pickup point.
4. The clients can check if there package has arrived at their pickup point and can pick their delivery up when they have the time for it.
For an autonomous delivery system the last step in this process is the most interesting. If there is an autonomous system that delivers the packages from a pickup point to the clients home it would save them time. This is especially true for areas where the density of pickup points is not so dense and clients would still have to travel some time to receive their orders.
The different price classes
The way the shipping cost of a package is determined depends on the weight of the package. Usually there is also a maximum size of length and width that the package needs to have. Lastly the shipping cost can be increased if it is requested that the package gets send with urgency. The price classes, based on weight, of PostNL for example are divided like this: [2 kg], [2-5 kg], [5-10 kg], [10-20 kg], [20-30 kg].[2]
The Main Stakeholder: PostNL
The main stakeholder of autonomous delivery systems is PostNL. PostNL a large post office in the Netherlands. In the Netherlands there are several other post offices that are in direct competition with PostNL. In order to move on with this competition it is necessary to deliver the packages and letters as efficiently and fast as possible, in order to meet the demands of the customers in the best way. Because the package delivery is growing in a fast pace thanks to the online shopping behavior of Dutch consumers [5]. PostNL has the biggest market share (50-60%) in the package delivery sector in the Netherlands [5]. For these reasons this sector is the most interesting for PostNL to invest in an innovation such as an autonomous delivery system.
PosgtNL current situation
In the current situation PostNL does not use any autonomous vehicles for the transportation of the packages. The package delivery proses has these following steps:
1. The client makes an order on a web shop
2. The package gets send from the web shops stockroom to a sorting centrum
3. The package is processed in the sorting centrum
4. The package is send to a pickup point close to the clients home
5. The client picks the package up from the pickup point
PostNL has 6 sorting centers in the Netherlands [6]. From these centers the packages are transported to the pickup points with large trucks. If the customer demands that the package is delivered to their house directly, the package is transported with a smaller van directly from the sorting center. Because of the low number of sorting center these vans usually have to traverse long distances and transport a lot less packages. In this process PostNL delivers 500.000 packages a day, during heyday this can increase to 1 million [7]. The pickup points in step 4 and 5 of the process are spread across the country, but in the more populated areas there are a lot more pickup points than in the smaller villages. In 2015 there were around 6,8 million people in the Netherlands that live in the big densely populated cities and around 6,5 million people on the rural eras. The rest of the population lived in a transition area between urban and rural [8]. The people that live in the urban areas do not have to look far for a pickup point and because the pickup points can provide for many customers in the neighborhood this is perhaps the most efficient way. But especially for the rural population the pickup points have to sustain customers spread over a large surface. Because there are still a significant amount of people living in these areas it is worth to improve the services in these areas.
Right now if customers choose to have their package delivered to their front door, the vans of the delivery company have to send a van with a very limited package capacity to an area where several customers expect an order. The van has to take the most optimal route to deliver the packages. The points in this process that an autonomous delivery system can improve are:
- costs of delivery employer
- costs of fuel for the van
- speed of delivery
- efficiency of delivery
References
[1] The self driving delivery robot, visited on the 8th of March 2017, visited from: https://www.washingtonpost.com/news/innovations/wp/2015/11/02/this-self-driving-delivery-robot-is-coming-soon-to-sidewalks/?utm_term=.3677b2f3536e ;
[2]The current prices for postal delivery, visited on 8th of March 2017, visited from: https://www.postnl.nl/tarieven/tarieven-pakketten/ ;
[3]The airship 600, visited on 16th of March 2017, visited from: https://en.wikipedia.org/wiki/Airship_Industries_Skyship_600 ;
[4]Costs of the Airship 600, visited on 16th of March 2017, visited from: http://www.newsday.co.tt/news/0,153096.html ;
[5] Autoriteit Consument & Markt, Pauline Gras, 20-05-2016, Nieuwsbericht: Online shoppen zorgt voor explosieve groei pakketvervoer Link: https://www.acm.nl/nl/publicaties/publicatie/15814/Online-shoppen-zorgt-voor-explosieve-groei-pakketvervoer/
[8] Volkskrant, niemand, 18 april 2016, nieuwsbericht: Meer mensen in stad dan op platteland http://www.volkskrant.nl/binnenland/meer-mensen-in-stad-dan-op-platteland~a767483/