# The Concept of Segmented Wind Turbine Blades: A Review
## 3 Transportation of Wind Turbine Blades  
In general, wind turbine blades are manufactured at a production facility and subsequently transported to the installation site [25]. Due to legislation differing between countries, the total number of transports and various other factors, transportation costs are highly route dependent. Every haul requires investigation of the optimal route and transportation method [26]. While wind turbine blades are frequently transported by road, typically, lengths of over 45 m need to be transported as oversized and overweight (OSOW) load requiring specialized trucks with rear steering escorted by service cars [27]. The route has to be analyzed to ensure blade transport vehicles can be accommodated [27]. Furthermore, modifications to the road may be required, and local regulations may restrict road transportation to nighttime, specific weather conditions and may impose special licenses [28; 29]. Licenses with a limited validity period introduce lead-times and additional costs in the case of a delay [30]. Wind turbine blades can also be transported by rail. While blade lengths are not limited to the size of a single rail car, trains have to go slower when part of the blade is hanging over board [31]. Further, blades are also transported over waterways and seas. However, to prevent twisting of the ship from damaging the blades, expensive fixtures, custom to every blade type, have to be used [29]. As a last resort, blades can also be transported by air lifters. Because helicopters are expensive and risky, blimp like air lifting devices are under development [26; 32]. Increased difficulty of transporting larger blades results in a non-linear increase in costs. Beyond certain breakpoints there is a sudden steep increase [26]. On the road, transportation costs rise sharply for blade lengths over 46 m and can be prohibitive for blades longer than 61 m [18]. Furthermore, there are actual limitations to the dimensions of components that can be transported for each method [33]. These apply to the bounding box surrounding the blade. As can be seen in Figure 1, the height and width of the box is determined by the blade's maximum chord length and the blade root diameter, as well as theamount of pre-bending and pre-curving. An overview of the maximum allowed dimensions and weights is given in Table 1.  
Various improvements have been made to the conventional transportation methods. One possible approach is to make the position in which the blade is carried variable. [PERSON] (1964) suggested a system where the blade is suspended at both ends, which can each be lifted. This allows the blade to be lifted over small obstacles. Similarly, [PERSON] (1980) suggested to rotate the blade to pass under obstacles such as bridges. These systems can be seen in Figure 2. Likewise, [PERSON] (1980) proposed connecting only the blade root to a truck with a system that enables tilting the tip upwards. This allows larger blades to get past a narrow corner. Furthermore, [PERSON] (1981) suggested tilting the blade and reducing the length of the carrying vehicle. Additionally, [PERSON] (1981) improved upon these tilting concepts, allowing the blade tip to be in front of the truck while using a lighter vehicle. To allow larger blades to be transported by rail, [PERSON] (1981) proposed using two coupled rail cars and using a sliding support. Another approach is to deform the blade to alter its dimensions. Modern wind turbine blades are often pre-curved and swept. For larger blades, however, the amount of pre-curving is less than desirable, due to the difficulty of transport [PERSON] (1981). This issue could be reduced by applying a load to \"straighten\" out the blades while they are transported [PERSON] (1981). In addition, to improve blade transportation by rail, [PERSON] (1981) advocated using bumpers to bend the more flexible outboard portion of the blades during turns so that there would be no overhang.