A lot of people use bicycle nowadays as a cheap and environment friendly transport. The cyclists are prone to accident. In the third world countries a lot of people die because of consuming more time in the emergency situation arising after these types of accidents. The object of this research is to design a safety helmet which can respond immediately on an emergency situation. It is done by integrating a MEMS (Microelectromechanical system) accelerometer, an SMS (Short Message Service) sending device, a gyroscope and a GPS (Global Positioning System) in an embedded system which is attached to the helmet. The system is activated if the biker falls prey to an accident and will send a text message to a predetermined number. The GPS helps to locate the biker. This smart helmet reduces the emergency response time after an accident to a great extent. On the other hand cost of the system would be affordable for bikers.
Keywords: Bicycle helmet, GPS (Global Positioning System), Embedded system
Bicycle is a common method of transport worldwide. Though bicycle was first invented in the 19th century, it wasn’t until 1975 when the first specialized helmet for bicycle was introduced. Bell Helmets of California, long known for its motorcycle helmets, introduced the celebrated Bell Biker with a thick Styrofoam-like shell and red straps.  It is well established that bicycle helmets protect against head, brain and facial injuries. This protection extends to crashes from a variety of causes (such as falls and collisions with fixed and moving objects) and includes crashes involving motor vehicles. Helmet use reduces the risk of head injury by 85%, brain injury by 88% and severe brain injury by at least 75%. Helmets should be worn by all riders whether the cyclist is a recreational rider or a serious competitor engaged in training or race competition. 
We also know that, Serious or fatal head injuries do occur despite use of an approved helmet. There is need for further research into the impact forces generated in riding accidents, and into the possibility of improving the performance of helmets. So, it is necessary to be prepared for these accidents.
The main problem after an accident is the time consumed to respond to the emergency call. The more the emergency response time is, the more the cyclist is under the risk of a major injury. An embedded system should be designed to reduce this emergency response time.
Moreover, suitable materials for the outer shell and the foam liner have to be selected. The design should be aerodynamically efficient.
2. Design of the embedded system:
An embedded system is a special-purpose system in which the computer is completely encapsulated by the device it controls. Unlike a general-purpose computer, such as a personal computer, an embedded system performs pre-defined tasks, usually with very specific requirements. Since the system is dedicated to a specific task, design engineers can optimize it, reducing the size and cost of the product. Embedded systems are often mass-produced, so the cost savings may be multiplied by millions of items.
The embedded system of the helmet consists of a MEMS (Microelectromechanical system) accelerometer, a gyro sensor, a GSM (Global System for Mobile Communications) module to send SMS (Short Message Service) and a GPS (Global Positioning System). The system is operated by a 5V dc source.
The GSM (Global System for Mobile Communications) module sends an SMS (Short Message Service) when the deceleration is equivalent to at least a 23 km/h (14 mph) barrier collision. If the vehicle does not cross that limit the system remains standby. Figure 2 of the following page outlines the system with a flowchart.
The prototyping can be done in Arduino with a V3.0 GPS/GPRS/GSM Shield and an InvenSense MPU-6050 sensor.
3. Design of the body of the helmet:
Bicycle helmets perform three functions:
♦ Reduces the deceleration of the skull and hence brain by managing the impact. This is achieved by crushing the soft material incorporated into the helmet;
♦ Spreads the area over which the forces of the impact reach the skull to prevent forces being concentrated on small areas of the skull; and
♦ Prevents direct contact between the skull and the impacting object.
These three functions can be achieved by combining the properties of the soft, crushable material that is incorporated into helmets – usually referred to as the liner, although it may be the only material of which the helmet is actually made – and the outer surface of the helmet, usually called the shell.
To work at all, the helmet has to stay on the wearer’s head during the impact phase. Helmets therefore have retention systems – usually a system of chin and neck straps – that are tested to ensure that they do not break and that they prevent the helmet rolling off the head when a force is applied upwards at the back of the helmet as can occur when a rider is sliding along the road.
EPS (Expanded polystyrene) will be used as the foam liner with 28 mm thickness and 55 kg/m3 density absorbing the impact of the accident efficiently.
The outer part of the three-dimensional liner will be converted to a shell, with its edge at the location of the real helmet shell edge. It will be assigned a Young’s modulus of 3 GPa, a Poisson’s ratio of 0.4, and an initial tensile yield stress of 60 MPa, which increases to 70 MPa at a strain of 1.0, data typical for polycarbonate. It was 0.4 mm thick, typical for bicycle helmets, and it was tying the liner exterior surface to simulate the ‘in-mould’ bonding process. 
Helmet straps will be made of nylon or polypropylene. A sample design is shown in figure 3
A smart helmet was designed successfully to reduce the emergency response time after an accident. This smart helmet can help the cyclists of the urban areas as well as those of the rural areas. As helmet is used in other vehicles and sports like motor cycles, skiing, snowboarding etc. the applications will become broader.
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