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53-446: A Driver Theory Test refers to a test taken when learning to drive . Countries that utilise a theory test as part of driver training are: Driving The term "driver" originated in the 15th century, referring to the occupation of driving working animals such as pack or draft horses . It later applied to electric railway drivers in 1889 and motor-car drivers in 1896. The world's first long-distance road trip by automobile

106-834: A certificate that proves the vehicle is safe and roadworthy . Also, it needs to have a minimum of third party insurance . Drivers may be required to take lessons with an approved driving instructor (or are strongly encouraged to do so) and must pass a driving test before being granted a license. Almost all countries allow all adults with good vision and health to apply to take a driving test and, if successful, to drive on public roads. In many countries, even after passing one's driving test, new drivers are initially subject to special restrictions under graduated driver licensing rules. For example, in Australia, novice drivers are required to carry "P" ("provisional") plates, while in New Zealand it

159-521: A locomobile , to the summit of Mount Washington in New Hampshire in the United States to generate publicity for their automobile. The 7.6-mile (12.2 km) journey took over two hours (not counting time to add more water); the descent was accomplished by putting the engine in low gear and much braking. Driving in traffic is more than just knowing how to operate the mechanisms which control

212-399: A constant speed ratio. The pitch circle of a given gear is determined by the tangent point contact between two meshing gears; for example, two spur gears mesh together when their pitch circles are tangent, as illustrated. The pitch diameter d {\displaystyle d} is the diameter of a gear's pitch circle, measured through that gear's rotational centerline, and

265-606: A driver's mental skills. Safety concerns in driving include poor road conditions, low visibility, texting while driving , speeding , impaired driving , sleep-deprived driving , and reckless driving . Laws regarding driving, driver licensing , and vehicle registration vary between jurisdictions. Most countries have laws against driving under the influence of alcohol or other drugs. Some countries impose annual renewals or point systems for driver's licenses to maintain road safety. The World Health Organization estimates that 1.35 million people are killed each year in road traffic; it

318-400: A gear train has two gears. The input gear (also known as the drive gear or driver ) transmits power to the output gear (also known as the driven gear ). The input gear will typically be connected to a power source, such as a motor or engine. In such an example, the output of torque and rotational speed from the output (driven) gear depend on the ratio of the dimensions of the two gears or

371-426: A pair of meshing gears, the angular speed ratio , also known as the gear ratio , can be computed from the ratio of the pitch radii or the ratio of the number of teeth on each gear. Define the angular speed ratio R A B {\displaystyle R_{AB}} of two meshed gears A and B as the ratio of the magnitude of their respective angular velocities: Here, subscripts are used to designate

424-464: A pitch circle radius of 2 in (51 mm), the angular speed ratio R A B {\displaystyle R_{AB}} is 2, which is sometimes written as 2:1. Gear A turns at twice the speed of gear B . For every complete revolution of gear A (360°), gear B makes half a revolution (180°). In addition, consider that in order to mesh smoothly and turn without slipping, these two gears A and B must have compatible teeth. Given

477-581: A traumatic brain injury). Some jurisdictions implement road space rationing , where vehicles are banned from driving on certain days depending on a variety of criteria, most commonly the letters and digits in their vehicle registration plate . A few countries banned women driving in the past. In Oman , women were not allowed to drive until 1970. In Saudi Arabia , women were not issued driving licenses until 2018. Saudi women had periodically staged driving protests against these restrictions and in September 2017,

530-405: Is a high rate of injury and death caused by motor vehicle accidents that involve teenage drivers. There is evidence that the less teenagers drive, the risk of injury drops. There is a lack of evidence as to whether educational interventions to promote active transport and share information about the risks, cost, and stresses involved with driving are effective at reducing or delaying car driving in

583-440: Is an integer determined by the pitch circle and circular pitch. The circular pitch p {\displaystyle p} of a gear can be defined as the circumference of the pitch circle using its pitch radius r {\displaystyle r} divided by the number of teeth N {\displaystyle N} : The thickness t {\displaystyle t} of each tooth, measured through

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636-407: Is called an idler gear. Sometimes, a single idler gear is used to reverse the direction, in which case it may be referred to as a reverse idler . For instance, the typical automobile manual transmission engages reverse gear by means of inserting a reverse idler between two gears. Idler gears can also transmit rotation among distant shafts in situations where it would be impractical to simply make

689-411: Is called restricted (R). Many U.S. states now issue graduated drivers' licenses to novice minors. While graduated driver licensing rules vary between jurisdictions, typical restrictions include newly licensed minors not being permitted to drive or operate a motorized vehicle at night or with a passenger other than family members, zero blood alcohol, and limited power-to-weight ratio of the vehicle. It

742-440: Is equivalently determined by the ratio of the number of teeth: In other words, the [angular] speed ratio is inversely proportional to the radius of the pitch circle and the number of teeth of gear A , and directly proportional to the same values for gear B . The gear ratio also determines the transmitted torque. The torque ratio T R A B {\displaystyle {\mathrm {TR} }_{AB}} of

795-405: Is given by This shows that if the output gear B has more teeth than the input gear A , then the gear train amplifies the input torque. In this case, the gear train is called a speed reducer and since the output gear must have more teeth than the input gear, the speed reducer amplifies the input torque. When the input gear rotates faster than the output gear, then the gear train amplifies

848-425: Is not connected directly to either the motor or the output shaft and only transmits power between the input and output gears. There is a third gear (Gear B ) partially shown in the upper-right corner of the photo. Assuming that gear is connected to the machine's output shaft, it is the output or driven gear. Considering only gears A and I , the gear ratio between the idler and the input gear can be calculated as if

901-423: Is possible for a driver to be suspended or disqualified (banned) from driving, either for a short time or permanently. This is usually in response to a serious traffic offence (for example, causing death due to drink driving), repeated minor traffic offences (for example, accruing too many demerit points for speeding), or for a specific medical condition which prevents driving, pending a future assessment (for example,

954-399: Is the gear ratio of the gear train, the input torque T A {\displaystyle T_{A}} applied to the input gear A and the output torque T B {\displaystyle T_{B}} on the output gear B are related by the same gear or speed ratio. The torque ratio of a gear train is also known as its mechanical advantage ; as demonstrated,

1007-620: Is the leading cause of death for people age 5 to 29. The origin of the term driver , as recorded from the 15th century, refers to the occupation of driving working animals , especially pack horses or draft horses . The verb to drive in origin means "to force to move, to impel by physical force". It is first recorded of electric railway drivers in 1889 and of a motor-car driver in 1896. Early alternatives were motorneer , motor-man , motor-driver or motorist . French favors " conducteur " (the English equivalent, " conductor ", being used—from

1060-459: Is the number of teeth on a gear divided by the pitch diameter; for SI countries, the module m {\displaystyle m} is the reciprocal of this value. For any gear, the relationship between the number of teeth, diametral pitch or module, and pitch diameter is given by: Since the pitch diameter is related to circular pitch as this means Rearranging, we obtain a relationship between diametral pitch and circular pitch: For

1113-499: The Vienna Convention on Road Signs and Signals standardises road signs, traffic lights and road markings to improve safety. The rules of the road, driver licensing and vehicle registration schemes vary considerably between jurisdictions, as do laws imposing criminal responsibility for negligent driving , vehicle safety inspections and compulsory insurance . Most countries also have differing laws against driving while under

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1166-472: The influence of alcohol or other drugs . Aggressive driving and road rage have become problems for drivers in some areas. Some countries require annual renewal of the driver's license. This may require getting through another driving test or vision screening test to get recertified. Also, some countries use a points system for the driver's license. Both techniques (annual renewal with tests, points system) may or may not improve road safety compared to when

1219-491: The pitch radius r {\displaystyle r} is the radius of the pitch circle. The distance between the rotational centerlines of two meshing gears is equal to the sum of their respective pitch radii. The circular pitch p {\displaystyle p} is the distance, measured along the pitch circle, between one tooth and the corresponding point on an adjacent tooth. The number of teeth N {\displaystyle N} per gear

1272-497: The rules of the road . Driving over a long distance is referred to as a road trip . In many countries, knowledge of the rules of the road, both practical and theoretical, is assessed with a driving test(s), and those who pass are issued with a driving license . A driver must have physical skills to be able to control direction, acceleration, and deceleration. For motor vehicles, the detailed tasks include: Avoiding or successfully handling an emergency driving situation can involve

1325-422: The 1830s—not of the driver but of the person in charge of passengers and collecting fares), while German influenced areas adopted Fahrer (used of coach-drivers in the 18th century, but shortened about 1900 from the compound Kraftwagenfahrer ), and the verbs führen , lenken , steuern —all with a meaning "steer, guide, navigate"—translating to conduire . The world's first long-distance road trip by automobile

1378-537: The Saudi government agreed to lift the ban, which went into effect in June 2018. Low gear A gear train or gear set is a machine element of a mechanical system formed by mounting two or more gears on a frame such that the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission of rotation from one gear to

1431-437: The angular rotation of all the gears in the gear train are defined by the angle of the input gear. The input torque T A {\displaystyle T_{A}} acting on the input gear A is transformed by the gear train into the output torque T B {\displaystyle T_{B}} exerted by the output gear B . Let R A B {\displaystyle R_{AB}} be

1484-433: The distant gears larger to bring them together. Not only do larger gears occupy more space, the mass and rotational inertia ( moment of inertia ) of a gear is proportional to the square of its radius. Instead of idler gears, a toothed belt or chain can be used to transmit torque over distance. If a simple gear train has three gears, such that the input gear A meshes with an intermediate gear I which in turn meshes with

1537-419: The drive gear ( A ) must make 1.62 revolutions to turn the output gear ( I ) once. It also means that for every one revolution of the driver ( A ), the output gear ( I ) has made 13 ⁄ 21 = 1 ⁄ 1.62 , or 0.62, revolutions. The larger gear ( I ) turns slower. The third gear in the picture ( B ) has N B = 42 {\displaystyle N_{B}=42} teeth. Now consider

1590-403: The driver and driven gear. If the driver gear moves in the clockwise direction, then the driven gear also moves in the clockwise direction with the help of the idler gear. In the photo, assume the smallest gear (Gear A , in the lower right corner) is connected to the motor, which makes it the drive gear or input gear. The somewhat larger gear in the middle (Gear I ) is called an idler gear. It

1643-515: The driver is not continuously or annually evaluated. Car ownership does not require a driver's license at all. As such, even with a withdrawn driver's license , former drivers are still legally allowed to possess a car and thus have access to it. In the USA, between 1993 and 1997 13.8% of all drivers involved in fatal crashes had no driver's license. In some countries (such as the UK), the car itself needs have

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1696-537: The following skills: Distractions can compromise a driver's mental skills, as can any altered state of consciousness . One study on the subject of mobile phones and driving safety concluded that, after controlling for driving difficulty and time on task, drivers talking on a phone exhibited greater impairment than drivers who were suffering from alcohol intoxication. In the US "During daylight hours, approximately 481,000 drivers are using cell phones while driving according to

1749-403: The gear ratio and speed ratio of a gear train also give its mechanical advantage. The mechanical advantage M A {\displaystyle \mathrm {MA} } of a pair of meshing gears for which the input gear A has N A {\displaystyle N_{A}} teeth and the output gear B has N B {\displaystyle N_{B}} teeth

1802-412: The gear ratio for the subset consisting of gears I and B , with the idler gear I serving as the input and third gear B serving as the output. The gear ratio between the idler ( I ) and third gear ( B ) R I B {\displaystyle R_{IB}} is thus or 2:1. The final gear ratio of the compound system is 1.62×2≈3.23. For every 3.23 revolutions of the smallest gear A ,

1855-415: The gear ratios of the two subsets are multiplied: Notice that this gear ratio is exactly the same as for the case when the gears A and B engage directly. The intermediate gear provides spacing but does not affect the gear ratio. For this reason it is called an idler gear. The same gear ratio is obtained for a sequence of idler gears and hence an idler gear is used to provide the same direction to rotate

1908-424: The gear train is defined as the ratio of its output torque to its input torque. Using the principle of virtual work , the gear train's torque ratio is equal to the gear ratio, or speed ratio, of the gear train. Again, assume we have two gears A and B , with subscripts designating each gear and gear A serving as the input gear. For this analysis, consider a gear train that has one degree of freedom, which means

1961-524: The gear train. The speed ratio R A B {\displaystyle R_{AB}} of the gear train can be rearranged to give the magnitude of angular velocity of the output gear in terms of the input gear velocity. Rewriting in terms of a common angular velocity, The principle of virtual work states the input force on gear A and the output force on gear B using applied torques will sum to zero: This can be rearranged to: Since R A B {\displaystyle R_{AB}}

2014-641: The gear, so gear A has a radius of r A {\displaystyle r_{A}} and angular velocity of ω A {\displaystyle \omega _{A}} with N A {\displaystyle N_{A}} teeth, which meshes with gear B which has corresponding values for radius r B {\displaystyle r_{B}} , angular velocity ω B {\displaystyle \omega _{B}} , and N B {\displaystyle N_{B}} teeth. When these two gears are meshed and turn without slipping,

2067-458: The gears will come into contact with every tooth on the other gear before encountering the same tooth again. This results in less wear and longer life of the mechanical parts. A non-hunting gear set is one where the teeth counts are insufficiently prime. In this case, some particular gear teeth will come into contact with particular opposing gear teeth more times than others, resulting in more wear on some teeth than others. The simplest example of

2120-437: The idler gear was the output gear. The input gear A in this two-gear subset has 13 teeth ( N A {\displaystyle N_{A}} ) and the idler gear I has 21 teeth ( N I {\displaystyle N_{I}} ). Therefore, the gear ratio for this subset R A I {\displaystyle R_{AI}} is This is approximately 1.62 or 1.62:1. At this ratio, it means

2173-468: The input torque. Conversely, if the output gear has fewer teeth than the input gear, then the gear train reduces the input torque; in other words, when the input gear rotates slower than the output gear, the gear train reduces the input torque. A hunting gear set is a set of gears where the gear teeth counts are relatively prime on each gear in an interfacing pair. Since the number of teeth on each gear have no common factors , then any tooth on one of

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2226-520: The next. Features of gears and gear trains include: The transmission of rotation between contacting toothed wheels can be traced back to the Antikythera mechanism of Greece and the south-pointing chariot of China. Illustrations by the Renaissance scientist Georgius Agricola show gear trains with cylindrical teeth. The implementation of the involute tooth yielded a standard gear design that provides

2279-490: The output gear B , then the pitch circle of the intermediate gear rolls without slipping on both the pitch circles of the input and output gears. This yields the two relations The speed ratio of the overall gear train is obtained by multiplying these two equations for each pair ( A / I and I / B ) to obtain This is because the number of idler gear teeth N I {\displaystyle N_{I}} cancels out when

2332-411: The pitch circle, is equal to the gap between neighboring teeth (also measured through the pitch circle) to ensure the teeth on adjacent gears, cut to the same tooth profile, can mesh without interference. This means the circular pitch p {\displaystyle p} is equal to twice the thickness of a tooth, In the United States, the diametral pitch P {\displaystyle P}

2385-578: The publication on the National Highway Traffic Safety Association. Another survey indicated that music could adversely affect a driver's concentration." Seizure disorders and Alzheimer's disease are among the leading medical causes of mental impairment among drivers in the United States and Europe. Whether or not physicians should be allowed, or even required, to report such conditions to state authorities, remains highly controversial. Safety issues in driving include: There

2438-421: The ratio of the tooth counts. In a sequence of gears chained together, the ratio depends only on the number of teeth on the first and last gear. The intermediate gears, regardless of their size, do not alter the overall gear ratio of the chain. However, the addition of each intermediate gear reverses the direction of rotation of the final gear. An intermediate gear which does not drive a shaft to perform any work

2491-428: The same tooth and gap widths, they also must have the same circular pitch p {\displaystyle p} , which means This equation can be rearranged to show the ratio of the pitch circle radii of two meshing gears is equal to the ratio of their number of teeth: Since the angular speed ratio R A B {\displaystyle R_{AB}} depends on the ratio of pitch circle radii, it

2544-401: The speed ratio, then by definition Assuming the gears are rigid and there are no losses in the engagement of the gear teeth, then the principle of virtual work can be used to analyze the static equilibrium of the gear train. Because there is a single degree of freedom, the angle θ of the input gear completely determines the angle of the output gear and serves as the generalized coordinate of

2597-509: The teenage years. Driveability of a vehicle means the smooth delivery of power, as demanded by the driver. Typical causes of driveability degradation are rough idling , misfiring , surging , hesitation , or insufficient power. Drivers are subject to the laws of the jurisdiction in which they are driving. Some jurisdictions submit to some or all of the requirements of the Geneva Convention on Road Traffic of 1949. Additionally,

2650-422: The vehicle; it requires knowing how to apply the rules of the road (which ensure safe and efficient sharing with other users). An effective driver also has an intuitive understanding of the basics of vehicle handling and can drive responsibly. Although direct operation of a bicycle and a mounted animal are commonly referred to as riding , such operators are legally considered drivers and are required to obey

2703-462: The velocity v {\displaystyle v} of the tangent point where the two pitch circles come in contact is the same on both gears, and is given by: Rearranging, the ratio of angular velocity magnitudes is the inverse of the ratio of pitch circle radii: Therefore, the angular speed ratio can be determined from the respective pitch radii: For example, if gear A has a pitch circle radius of 1 in (25 mm) and gear B has

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2756-687: Was in 1888, when Bertha Benz drove a Benz Patent-Motorwagen from Mannheim to Pforzheim , Germany. Driving requires both physical and mental skills, as well as an understanding of the rules of the road. In many countries, drivers must pass practical and theoretical driving tests to obtain a driving license. Physical skills required for driving include proper hand placement, gear shifting, pedal operation, steering , braking , and operation of ancillary devices. Mental skills involve hazard awareness, decision-making, evasive maneuvering, and understanding vehicle dynamics . Distractions , altered states of consciousness , and certain medical conditions can impair

2809-708: Was in August 1888, when Bertha Benz , wife of Benz Patent-Motorwagen inventor Karl Benz , drove 66 mi (106 km) from Mannheim to Pforzheim , Germany , and returned, in the third experimental Benz motor car, which had a maximum speed of 10 mph (16 km/h), with her two teenage sons Richard and Eugen but without the consent and knowledge of her husband. She had said she wanted to visit her mother, but also intended to generate publicity for her husband's invention, which had only been taken on short test drives before. In 1899, F. O. Stanley and his wife Flora drove their Stanley Steamer automobile, sometimes called

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