The crane for lifting heavy loads was invented by the Ancient Greeks in the late 6th century BC "essay_footnotecitation_link">1] . The archaeological record shows that no later than c.515 BC distinctive cuttings for both lifting tongs and lewis irons begin to appear on stone blocks of Greek temples. Since these holes point at the use of a lifting device, and since they are to be found either above the centre of gravity of the block, or in pairs equidistant from a point over the centre of gravity, they are regarded by archaeologists as the positive evidence required for the existence of the crane  .
Cranes are some of the most useful and widely operated items of plant on construction sites. However, if misused, they can cause serious harm. There is no other item of construction equipment which has the capacity for causing as much damage or injuring so many people as does a crane in an accident. Most serious accidents involving cranes are a result of inadequate planning and unsafe use leading to instability and overturning. All site engineers, managers and supervisors who are involved in the specification, installation or use of cranes on site, must be aware of the fundamental criteria, planning issues and checks that are needed to ensure lifting operations proceed in a logical, safe and stable manner.
Tower Cranes are suitable for semi-permanent installation for covering large areas whilst taking up relatively little room at ground level, hence their suitability for city centre use of the type indicated in this assignment. An example of a typical luffing crane is shown below,
BS 7121 is the British Standard Code of Practice for the Safe Use of Cranes. It is recognised as best practice in the industry and has been drawn up by the industry in conjunction with the Health and Safety Executive (HSE). HSE recommends the use of BS7121 to any person or organisation who have duties under the Health and Safety at Work Act 1974 and who use or hire cranes. As with all workplaces, The Health and Safety at Work Act 1974, referred hereafter as The Act, is the primary piece of legislation that is applicable in this instance, and Part 1 sets out the
"General Duties" of an employer towards his employees. Section 2(1) says:-
"It shall be the duty of every employer to ensure, so far as is reasonably practicable, the health, safety and welfare at work of all his employees." 
Sub-Section 2 requires, inter alia, the provision and maintenance of plant and systems of work that are, so far as is reasonably practicable, safe and without risks to health.  It is also incumbent upon the employer, under Section 3 of The Act to ensure that he does not conduct his undertaking so as not to impose persons other than his employees to risks to health and safety, and finally Section 7 of The Act places a duty on employees to take reasonable care for the health and safety of themselves and of others whom they may affect. 
Whilst compliance to the code does not in itself confer immunity from legal obligations, failure to comply would be taken as prima facie evidence of failure to provide a safe place of work for employees and contractors. The code also gives guidance on how to comply with Lifting Operations and Lifting Equipment Regulations 1998 and the Provision and Use of Working Equipment Regulations 1998. LOLER builds on the requirements of PUWER, which requires, inter alia, duty holders to provide suitable work equipment for the task information, instructions and training to the people who use it, and information on stability. It is therefore important to remember that duty holders who provide lifting equipment, in addition to complying with LOLER, will also need to comply with all relevant aspects of PUWER. 
In accordance with the recommendations of BS 7121 Pt1, and as part of the statutory obligations described above, a full risk assessment will need to be undertaken, in order to identify the hazards associated with the intended operation. The assessment should evaluate the risks involved and the nature and extent of any measures required to mitigate those risks. The appointed person should also take into consideration hazards identified by the overall site risk assessments. 
The guidance does go on to say that a generic risk assessment is unlikely to be sufficient since most sites have hazards that are unique to that situation, and these should obviously be taken into account in the form of a site specific assessment. Once the risk assessment has been carried out, a full method statement needs to be prepared, detailing the safe system of work for the lifting operation.
Part 1 gives general guidance and recommendations on the use of cranes whilst Part 3 deals specifically with the use of mobile cranes.
BS7121 makes a clear distinction between Crane Hire, where the Hirer has responsibility for the planning and organisation of the lifting operations and Contract Lifting where the main responsibilities of planning, organizing and supervising the lifting operation are contracted out to the Crane Owner. A summary of the respective responsibilities are:
Crane Hire: The Hirer must:
Plan the lift and operate a safe system of work
Supply the Appointed Person
Carry out all work in accordance with BS7121
Ensure all equipment used is tested and certified and free from any visible defects
Contract Lift: The Crane Owner must:
Plan the lift and operate a safe system of work
Supply the Appointed Person
Carry out all work in accordance with BS7121
Ensure all equipment used is tested and certified and free from visible defect
Outside the scope of BS7121 are the different insurance arrangements within Crane Hire and Contract Lifting. Under Crane Hire the Hirer must insure the operator and crane under third party liability and hired in plant policies. With certain exclusions these are covered under Contract Lift terms.
The Notification of Conventional Tower Cranes Regulations 2010 (the 'Regulations') come into force on 6 April 2010. The Regulations require certain information about conventional tower cranes used on construction sites to be notified to the Health and Safety Executive (HSE). The Regulations require conventional tower cranes used on construction sites to be notified to HSE. A conventional tower crane is defined in the Regulations as a 'slewing jib type crane with jib located at the top of a vertical tower and which is assembled on a construction site from components'  .This includes, but is not limited to, such cranes with horizontal or luffing jibs and slewing rings at the base or top of the tower. These tower cranes are usually installed (and dismantled) with the assistance of another crane and, as a result, are sometimes referred to as 'assisted erected cranes'. All conventional tower cranes erected on construction sites  need to be notified to HSE. That is, all such cranes used to construct new buildings and structures or refurbish or demolish existing ones. The duty to notify does not apply to other types of tower cranes such as self-erecting tower cranes  or any other types of crane, eg mobile cranes. Nor does the duty apply to tower cranes on sites other than construction sites.
Safe Systems of Working (SSW)
Once the Risk Assessment has been completed a full Method Statement should be prepared detailing the safe system of work for the operation. This should include:
The task to be achieved
Configuration of the crane at the end of the task
Steps to eliminate danger to personnel not involved in the lift
Clear statements of responsibilities and roles for each member of the team
Any site induction requirements
Selection of Personnel: BS7121 sets out guidance for the selection of personnel to carry out the lifting operation and details the minimum attributes, competencies and experience. All personnel must be trained and competent in the use of the crane signalling as recommended in BS7121 which has become an industry standard. 
Planning should take account of the effect that long working hours can have on the concentration of personnel engaged in the operation of tower cranes and ensure that the work is adequately resourced to allow rest breaks to be taken. Table 1 gives the minimum number of operators required for continuous single shift operation of a given number of tower cranes  .
It also sets out detailed requirements for the training of operatives. All personnel should be:
Trained and assessed
Able to present a record of training and assessment
Physically able to do the work
The radius over which a crane has to lift will have a significant effect on the loads that can be lifted and to what height they can be lifted. Table A, below, for a particular type of crane, illustrates this point  :
Tabel A: Illustrating the relationship between lifting capacity and lifting radius
The basic requirements, relating to SSW of BS7121 are:
Safe System of Work: This should include:
Planning of the operation
Selection of the crane and suitable lifting equipment
Preparation of the site
Examination of the crane and equipment
Provision of properly trained and competent operatives and supervision
Examination of test and other documentation
Prevention of unauthorized movement or use
Safety of persons not involved in the lifting operations
The code requires that all lifting operations are planned and that foreseeable risks have been taken in to account. Planning of the lift should include  :
Taking in to account the load, its characteristics and the method of lifting
The selection of a suitable crane
The selection of suitable lifting equipment
The position of the load before, during and after the lifting operation
The site, including space available and proximity hazards
Environmental conditions e.g. inclement weather
Flow of information between personnel involved in lifting operations 
Eight deaths have been linked to tower cranes in the past decade in the U.K. alone, with the rest of the world having similar issues.
Dec. 14, 2007, New York: A crane drops seven tons of steel on a construction trailer, critically injuringan architect.
March 15, New York: A 19-story crane breaks away from an apartment tower under construction, demolishes a townhouse, damages several other buildings & six construction workers, the crane operator, & a tourist are killed.
March 25, Miami: A crane at a condo project falls 30 stories onto a home killing two workers and injuring five.
May 20: Adair: A crane replacing a bridge on an interstate highway topples on to rail tracks, killing the operator.
Canada - two firms with fines totalling $315,343.71 for their part in the death of a crane operator.
UK - Two fatal accidents at construction sites in the same weekend.
China - 5 Die, 91 Hurt As Crane Crashes On School.
Australia - 4 dead, 2 injured in crane collapse at rail construction site.
Vietnam - Crane collapse kills seven.
India - Construction worker killed when crane being used to lift materials collapses  .
The hazards associated with this type of operation are well documented, and covered within the various standards, guides and codes of practise. However, because the work is being carried out within a city centre site, it is important to recognise that there will be additional hazards:
Underground hazards: for example basements, sewers, tunnels, live services, poorly back-filled trenches, manholes and inspection chambers. All of the above can affect the stability of the crane,
Ground conditions: there has to be an accurate assessment of ground conditions,  including the location of any water courses,
Distance of the crane from the structure under construction, and in particular the location of adjacent buildings, roads and pedestrian access points,
Wind conditions: there are several factors that need to be considered with regards to the prevailing weather conditions, in particular the impact of adjacent buildings on the direction of the wind. Wind is a huge potential problem with respect to the use of a tower crane, and the control measures in the next chapter outline the precautions that need to be considered,
Adverse weather conditions such as snow and ice also need to be taken into consideration, particularly at this time of year,
Overhead cables or other proximity hazards must also be considered,
The route to and from the site, particularly given its location, must be carefully considered. Attention should also be given to vehicles that will be delivering the loads for the crane.
By considering the hazards above, it is possible to implement sufficient control measures that will ensure that the lifting operations can proceed, and that a safe system of work can be established.
It is vital to ensure that the capacity of the crane is sufficient for the lifting operations that are proposed.
The relevant Local Authority and Utility providers should be contacted in order to obtain all the requisite information on any underground hazards,
When working in city centres, arrange for lorry access onto site so that there is no public interface when lifting off the load, and when working adjacent to a public highway, organise the works so that crane jibs always face away from, or are parallel to, the road, 
To mitigate the effects of the wind, it is recommended to introduce a system of monitoring wind speeds. The DTI guidance recommends the following table for the use of tower cranes.