An equal-tangent vertical curve with an entry grade of +1.0% and a final grade of -2.0% was designed in the year 2008 to accommodate a speed of 110km/h. In that year, design deceleration rate and the perception- reaction time was considered to be 3.2m/s? and 2.0seconds respectively. 14 years later (2022), the curve is to be redesigned to still accommodate a speed of 110km/h. However, vehicle performance characteristics such as braking efficiency have increased over the period, such that the new recommended design deceleration rate is now 25% greater than the value utilised in the 2008 design. Meanwhile, the population of older drivers have now increased such that the design perception-reaction times is now 30% higher than
An equal-tangent vertical curve with an entry grade of +1.0% and a final grade of -2.0% was designed in the year 2008 to accommodate a speed of 110km/h. In that year, design deceleration rate and the perception- reaction time was considered to be 3.2m/s? and 2.0seconds respectively. 14 years later (2022), the curve is to be redesigned to still accommodate a speed of 110km/h. However, vehicle performance characteristics such as braking efficiency have increased over the period, such that the new recommended design deceleration rate is now 25% greater than the value utilised in the 2008 design. Meanwhile, the population of older drivers have now increased such that the design perception-reaction times is now 30% higher than
Chapter2: Loads On Structures
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Transcribed Image Text:An equal-tangent vertical curve with an entry grade of +1.0% and a final grade of -2.0% was designed in
the year 2008 to accommodate a speed of 110km/h. In that year, design deceleration rate and the perception-
reaction time was considered to be 3.2m/s² and 2.0seconds respectively. 14 years later (2022), the curve is
to be redesigned to still accommodate a speed of 110km/h. However, vehicle performance characteristics
such as braking efficiency have increased over the period, such that the new recommended design
deceleration rate is now 25% greater than the value utilised in the 2008 design. Meanwhile, the population
of older drivers have now increased such that the design perception-reaction times is now 30% higher than
the value for 2008. Also, vehicles have now become smaller, such that the driver's eye height is now taken
to be 900mm above the road surface compared to 1.10m in 2008. Similarly, roadway objects (such as
vehicle tail-lights) are now assumed to be 300mm above the surface compared to 600mm in 2008.
a) Determine the minimum required lengths of curve for the 2008 and 2022 designs.
b) How has the changing design parameters affected the 2022 design?
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