A head on crash is very severe when compared to other types of highway crashes. It takes just a few seconds for vehicles moving at highway speed to cross the median and collide with the vehicles from the other side of the lane. Median barriers are effective in separating the opposing traffic streams of a road physically. It also helps to stop vehicles moving into the opposite lane accidentally and to avoid pedestrians crossing the road at risky places. In 2006 there were 821 median cross over accidents that resulted in fatalities on U.S National highway system alone.
™
The factors that influence the selection of a barrier system are the type of the vehicles involved, roadway geometry and the potential severity of any head on crash incident. In most locations a standard barrier capable of redirecting the vehicles to the right area would suffice. However, in locations with complex geometry, adverse environmental conditions, heavy truck traffic and high traffic volumes and speeds, a barrier with high performance is necessary.
There are basically three categories of median barriers. They are detailed below,
Rigid barriers
The most common type of the median barrier in use today is optical easy the concrete barriers.
Pros:
- They are widely used because of their maintenance free characteristics, low life cycle cost and safety performance.
- They are very effective in avoiding vehicle crossover collision on accident prone regions with high traffic volumes and speed.
- They can also be used in areas where the required median widths to install other types of barriers is not available.
- Jersey barrier is a modular concrete barrier that allows the vehicles to collide on its lower slopped face, pivoting it back in its original direction.
Cons:
- Comparatively the installation cost of rigid barriers is high.
Semi rigid barriers
It is otherwise called as guardrail or guiderail. These rails are made of metals and they are collected in segments supported by posts or blocks.
Pros:
- Unlike rigid barriers, semi rigid barriers are designed to absorb more energy from the impact and the entire assembly move or deflect during the crash. Hence, lesser damage to the vehicle.
- Installation cost is less.
Cons:
- They are only suitable in the areas that are not sloppy and have good soil condition.
- The cost of the repair following an impact is high.
Cable barriers
Typically it consists of multiple cables that are connected to each other in a series of posts.
Pros:
- It is the most versatile and forgiving barrier system in minimizing the median crossover crashes. This absorbs most of the energy of the impact and reduces the forces exerted on the vehicles and its occupants.
Cons:
- Considerable time and cost must be spent maintaining, endangering motorists and workers during each repair.
The other factors that are considered before deciding the barrier type are road alignment, crash history and the number of lanes.
The vector images are defined mathematically, based on their geometric characteristics. To be precise, a vector image is described by a set of geometric primitives that describe points, lines, curves, and polygons to which we can attribute colors and shades. They are radically different from raster images, which are described as a grid of properly colored pixels.
Advantages
1. In most cases, vector images will require lesser disk space than a bitmap. They are mostly formed by flat colors or simple gradients because of which they do not require a lot of disk space. Lesser the information to create the image, smaller is the file size. Thus, they are given more preference in comparison to other images.
2. Vector images do not lose quality when they are scaled. In principle, a vector image can be scaled indefinitely. In the case of matrix images, a point is reached where it is evident that the image is composed of pixels. Thus, the quality of vector images is superior to other forms of images.
3. They can be easily saved and modified in the future. The best part is that, the process of modification is quite simple as well. All kinds of changes can be easily managed without any difficulty. Even if a file is modified, the resultant file does not occupy a lot of space. This is another reason why they are used across industries.
4. The process of creating them is quite simple as well. In fact, using simple drawings we can get complex vector images without a lot of difficulty. Simple and user-friendly programs such as Macromedia Freehand, Corel Draw and Adobe Illustrator can be used for creating simple drawings, which can be converted to vector images.
Disadvantages
1. They are generally not suitable for encoding pictures or videos taken in the "real world" (for example - photographs of nature), although some formats support a mixed composition. Virtually all digital cameras store images in bitmap.
2. The data used to describe them must be processed by a powerful machine, i.e. the computer must be powerful enough to perform the necessary calculations for forming the final image. If the data volume is high it may slow down the rendering of the image on screen, even when working with small files.
3. Another disadvantage is that, even small drawing errors are often visible, when the images are enlarged to certain extent. Such an incident can affect the quality of the images, especially when they are used in the field of animation.
Despite the fact that vector images have a few disadvantages, they have a wide range of applications and are implemented in the fields of computer graphics, architecture and engineering etc.