Parking and security bollards are a vital part of estate management for many venues and buildings, allowing for a pedestrianised area that is still accessible to vehicles when necessary. Private parking spaces, especially in big cities and commercial estates, are often protected by a moveable bollard that allows the parking space owner to shut off their space when it is not being used. Some of these parking bollards are of a style that simply fold over at the base, locking into position with a key, but the hydraulic style, that rise and descend flush with the ground are much more secure and are ideal for use outside offices and venues where emergency services or deliveries may need access close to the building, but for the most part it is left as a pedestrian zone. Hydraulic retractable bollards are becoming popular with domestic users who want to protect their driveways. People who live in areas where sporting events take place can find that visitors park on their driveway or in front of it, blocking their own access. Similarly, people with driveways in big cities can find opportunistic parkers in their spot at weekends and seasonal big shopping days and opt to install a hydraulic bollard to keep their driveways clear. An electro-hydraulic bollard cannot be tampered with, so while a folding style could be broken or unbolted by someone determined to park on a driveway, an electro-hydraulic one will deter,, even the most insistent problem parker. Hydraulic security bollards can be designed to be much larger, both in height and width, than a folding style, and because many are electro-hydraulic they can be wired into an access system which allows parking space owners, renters or security staff to lower and raise them via remote control, RFID tag, pre-payment meters, keypads or proximity sensors on the vehicle itself. Of course, they do require more installation than a folding style, as they must be dug into the ground and secured that way, rather than being bolted directly to the ground. Hydraulic bollards typically take between seven and three seconds to descend or raise, but many models are fitted with a pressure relief valve that acts as an emergency lowering system when a quick exit is needed, or perhaps to allow emergency vehicles in quickly and at the last minute, preventing other vehicles from entering the area while waiting. A hydraulic power pack drives the hydraulic ram, which is fitted within the bollard casing, allowing for raising and lowering of the equipment on demand. For easy maintenance, the hydraulics are usually located centrally within the assembly, rather than right at the bottom of the equipment. Hydraulic bollards are specifically designed for regular use with low maintenance, and as such the oil can be a hardwearing type suitable for use at normal weather temperatures, but of course the oil will need to be changed at some stage and maintenance or repairs may be needed as well. Locating the moving gear at an accessible height means maintenance can be carried out easily when needed. This means that the hydraulic power pack must be capable of effecting motion in both directions, so it can lower and raise from a central position. Other types of retractable bollard are available, such as electro-mechanical and electro-pneumatic, however, the hydraulic options are stronger and more resistance to impact forces than these other types, making them a much more desirable option where impacts are likely. In busy streets, a bollard may well be reversed into accidentally, but a hydraulic model will withstand that impact without damage. In sensitive areas, or those likely to be the target of a vehicle based attack, a strong hydraulic retractable bollard will provide much more protection to the people and building they are protecting than a mechanical or pneumatic option, so electro-hydraulic retractable bollards are becoming the obvious choice for protecting both property and people.