**7.1 Stopping sight distance (SSD)**

The distance traveled by the vehicle from the instant the driver sights an object necessitating a stop to the instant the brakes are applied and the distance required to stop the vehicle from the instant brake application begin or defined as the sum of distances from when the driver decides to apply the break until the car stop, as in Eq. (1):

$$\text{SSD} = \{0.278 \times \text{V} \times \text{t}\} + \{0.039 \times \frac{\text{v}^{\text{i}}}{\text{a}}\} \tag{1}$$

where (SSD) is the stopping sight distance in m, (V) is the initial speed (kph), (a) is the rate of deceleration (3.4 m/S2), and (t) is the Brake reaction time, which is assumed to be 2.5 seconds by AASHTO [11].

**Table 3** can illustrate the stopping sight distance and its relation to the design speed, brake reaction distance, and braking distance on level. **Table 4** illustrates increment of the stopping sight distance and its relation to the design speed and brake in state of slope directed down [12–14].


#### **Table 3.**

*Stopping sight distance and its relation to the design speed and brake [12].*


#### **Table 4.**

*Relationship between design speed and increment of stopping sight distance in state of downslope [15].*

**127**

*Building an Integrated Database of Road Design Elements*

**Passed vehicle**

*DOI: http://dx.doi.org/10.5772/intechopen.88678*

**Design speed (km/h)**

**7.2 Passing sight distance (PSD)**

*Passing sight distance for the design of two-lane highways [16, 17].*

**7.3 Horizontal planning of the road**

passing vehicle [16].

**Table 5.**

factors as follow [18]:

human factor.

It represents enough free distance of traffic so that the driver can see the driver in front of him to be able to complete the process of circumventing without touching the car that passes without being intercepted by any counter vehicle may appear after the start of the bypass and then return to the right warm easily after the overtaking process. PSD is designed for two-lane highway as in **Table 5** which illustrate passing sight distance with respect to the design speed for passed and

**Assumed speed (km/h) Passing sight distance (m)**

**From exhibit 3–6**

**Rounded for design**

**Passing vehicle**

 29 44 200 200 36 51 266 270 44 59 341 345 51 66 407 410 59 74 482 485 65 80 538 540 73 88 613 615 79 94 670 670 85 100 727 730 90 105 774 775 94 109 812 815

The horizontal curve is a part of circular curves, which consist of intersection of two tangents of road. Horizontal curve has four types illustrated in **Figure 1**. The location and configuration of the horizontal curve are affected by some of the

1.Physical condition: land uses, earth topography and geophysical conditions,

2.Environmental circumstances: impacts on the adjacent land use, community-

3.Economics condition: cost of construction, road ownership costs, effects of

4.Road safety: distance of sight, alignment consistency, considerations of the

5.Classification and design considerations of highway: level of service, func-

intersection with waterway and man-made barriers.

based impacts, and environmentally sensitive areas.

utility, costs of operating, and maintenance.

tional classification, design speed, and standards.


*Building an Integrated Database of Road Design Elements DOI: http://dx.doi.org/10.5772/intechopen.88678*

**Table 5.**

*Geographic Information Systems in Geospatial Intelligence*

SSD = (0.278×V×t) + (0.039 × v

assumed to be 2.5 seconds by AASHTO [11].

brake in state of slope directed down [12–14].

**Brake reaction distance (m)**

*Stopping sight distance and its relation to the design speed and brake [12].*

**Design speed (Km/h)**

**7.1 Stopping sight distance (SSD)**

**7. Specifications and determinants of roads' design and general criteria**

The distance traveled by the vehicle from the instant the driver sights an object necessitating a stop to the instant the brakes are applied and the distance required to stop the vehicle from the instant brake application begin or defined as the sum of distances from when the driver decides to apply the break until the car stop, as in Eq. (1):

> 2 \_

where (SSD) is the stopping sight distance in m, (V) is the initial speed (kph), (a) is the rate of deceleration (3.4 m/S2), and (t) is the Brake reaction time, which is

**Table 3** can illustrate the stopping sight distance and its relation to the design speed, brake reaction distance, and braking distance on level. **Table 4** illustrates increment of the stopping sight distance and its relation to the design speed and

> **Braking distance on level (m)**

 13.9 4.6 18.5 20 20.9 10.3 31.2 35 27.8 18.4 46.2 50 34.8 28.7 63.5 65 41.7 41.3 83.0 85 48.7 56.2 73.4 129 55.6 73.4 129.0 130 62.6 92.9 156.5 160 59.5 114.7 184.2 185 76.5 138.8 215.3 220 83.4 156.2 248.5 250 90.4 193.8 284.2 285

**Design speed (km\h) Increase the stopping sight distance in state of downslope (m)**

40 2 4 6 50 3 6 10 60 5 10 18 70 7 15 6 80 9 21 - 90 12 29 - 100 16 38 -

*Relationship between design speed and increment of stopping sight distance in state of downslope [15].*

**3% 6% 9%**

*<sup>a</sup>* ) (1)

**Stopping sight distance Calculated (m) Design (m)**

**126**

**Table 4.**

**Table 3.**

*Passing sight distance for the design of two-lane highways [16, 17].*
