**lecture notes of chapter five :**

** Horizontal Alignment **

**The Transition Curves**

**Widening and superelevation**

** Sight Distance on Horizontal Curves**

**Exercises**

**1- A circular curve is used to join two horizontal directions. The curve was widened to provide a suitable operation condition. The design speed on the curve=60km/hr, radius of the curve=80m, f _{s }=0.15, design wheel base=6.1m**

**1- if the highway width at point (1)= 7m find the highway width at point( 2)**

** 2- if the elevation at the edge (A)=10m find the elevation at the edge (B) **

**2-The figure shows a two lane highway in a hilly area. A rock located at a distance of 3m from the C.L of the inside lane obstructs the sight distance. If the radius to the C.L of the inside lane =40m, assuming a flat highway section, calculate the allowable speed on this section of the highway. ( coef. of friction=0.3, perception- reaction time=2.5 sec) **

**3- Prepare a setting out table to set out a spiral curve every 20m using the following data:**

** Length of spiral =100m. Radius of the circular curve= 400m**

** Station P.I = 20+00 (station of the intersection point between the two **

** tangents) Deflection angle between the two tangents =40 ^{º}**

**4- Determine the minimum distance an object can be placed from the inside edge of a two lane flat highway without reducing the required stopping sight distance. The design speed=70km/hr, lane width=3.5 m, radius to the centerline of the highway=100m perception-reaction time= 2.5 sec, f=0.3 **

**5- A horizontal curve of radius=100m is used to connect two tangents. The deflection angle between the tangents= 80˚ , station I= 20+15 ,**

**1- prepare a setting out table to set out the curve at points every ½ station.**

**2- If the design speed on the curve = 50 km/hr, f _{s }=0.15, calculate the rate of superelevation on the curve.**

**6- C1 and C2 are two horizontal circular curves joined by a straight segment**

**Find stations PC1,PT1,PC2,PT2 .Find the length of the straight segment **

**Prepare a setting out table to set out the curve C1 every ½ station**

** An object is located at a distance of 2m from the C.L of the inside lane .What should be the design speed to provide minimum S.S.D**

**Assuming a horizontal highway segment. Lane width=3m**

**7-**

** Complete the following sentences**

**1-low fill slope range= **

**2-shoulder slope range=**

**3-mountable curb height should be <**

**4-on motorways the maximum grade =**

**5-minimum grade on curbed pavement highway =**

**6-maximum length of spiral curve depends on…**

**8- A circular horizontal curve is used to connect two intersecting tangents.**

** The deflection angle between the tangents= 45˚, the length of the curve=400m.**

** Station P.T=30+00,**

**1- prepare a setting out table to set out this curve at every 1/2 station.**

**2- if the elevation of point P.C=100m, elevation of P.T.= 108m and the curve **

**has uniform slope, calculate the elevations on this curve every ½ station.**

** 3-In order to improve the alignment of this curve, a transition curve is **

** suggested. A shift value= 1.5 m is decided, calculate the required length**

** of this transition curve and find station TS.**

**9- State whether the following sentences are true or false. Correct the sentence if **

** false.**

**1- when speed > 25km/hr, design is controlled only by the minimum turning path of the design vehicle.**

**2- best alignment is achieved when intersecting roads meet at an angle=40˚**

**3- when traffic light is used to control traffic the intersection is called interchange.**

**4- the traveled way on the horizontal curves are widened to increase the capacity **

** of the highway.**

**5- compound curves are used to change the alignment of the highway.**

**6- simple circular curves are used as vertical curves to connect two grades.**

**7-superelevations must be used at intersections inside towns.**

**10- a circular curve horizontal ramp is used to connect two intersecting highways. The deflection angle between tangents =50 degree.The length of the ramp=90m,superelevation rate=4% , f _{s }=0.15, f=0.3,**

**perception reaction time = 2.5sec.**

**1- find the speed limit on this ramp.**

** 2-using this speed limit calculate the minimum stopping sight distance. **

**11- A large object is located at a distance if 3m from the centre line of the inside lane of a horizontal curved section of a highway. This object affect the required stopping sight distance. The radius to the centre line of the inside lane=200m. Calculate the maximum speed on this highway to ensure safe crossing of pedestrians. Assume G=0**

**12-The figure shows a highway circular ramp connecting point A to B. The length of the ramp=235.62m. The superelevation rate =0.06, find:**

**a- the speed limit on this ramp**

**b-using this speed limit calculate the minimum stopping sight distance **

** **