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.
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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 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.
Anyone who has added a pond or water garden to their property is probably enjoying the beautification benefits such an addition provides. After all, how could exotic goldfish or aquatic plants not improve visual allure? Of course, plants and fish have to be visible in order to provide that benefit. When they are obscured or, worse, harmed by algae these benefits decrease. That is why removing algae are important. The most popular way to remove algae is through the use of algaecides. While this is a good method, it is not a perfect one. So, let's look at a few of the pros and cons of using algaecides.
Cons
· Some algaecides such as copper sulfate can cause harm to certain fish like koi that may live the pond. This is why it is necessary to select an algaecide that has a good reputation in the consumer marketplace. Also, if the algaecide comes in granular form it needs to dissolve as soon as it comes in contact with the water. If not, it could possible be ingested by birds or pets. This could poison the animal.
· Using too much algaecide or using 散光日拋價格 it in a new pond prior to proper development of an adequate ecosystem can have devastating effects. One of these effects could be an inordinate increase of ammonia in the pond while simultaneously decreasing helpful bacteria in the pond. Needless to say, this can harm plant and aquatic life.
· Some algaecides can be mildly corrosive. That is why they should not be mixed with ammonia, household cleaners, or other products that would increase the potential for corrosiveness to the pond. Also, there is the potential that liquid algaecides can burn flesh if not handled properly. That is why extreme care must be taken when handling algaecides.
· Algaecides or only a short-term solution. Typically the use of an algaecide will only temporarily kill off the algae, only to create a food source for a new algae bloom. Algaecides should be used in conjunction with beneficial pond bacteria and good filtration to help remove the resulting dead algae.
Pros
· Algaecide is proven to eliminate algae easily and inexpensively. For many pond owners, the need for an effective algae treatment must coincide with one that is simple to use and does not cost very much. Thankfully, there are a number of quality algaecides on the market that deliver on both these fronts.
· Algaecides, work in a quick and efficient manner. In fact, there are algaecide formulas, which can eliminate algae within 24 hours. This is no minor point. Algae can cause a great deal of havoc in a pond and the ability to eradicate it as soon as possible is helpful.
· Many algaecides are fish and plant safe, such as GreenClean. In the past people primarily were using copper products, which can be harmful to fish if not used precisely.
Can ponds look good without algaecide use? Absolutely. However, algaecides can work wonders as one of many tools used for keeping a pond or water garden in proper condition. In general, algaecides are harmless although one needs to understand certain potential problems. But, if algaecide is used properly, most algae related problems can be averted.