Roadway Capacity In Highway Design

Roadway Capacity depends on the traffic volume. Traffic volume can be served at each level of service are referred to as "Service flow rate".Once each level of service has been chosen for particular design, the corresponding service volume logically becomes the 'design service volume'. It indicates that if the traffic volume using the facility exceeds design service volume, the operating conditions of the roadway will be in inferior to the level of service. The level of service appropriate for various various type of roadways are given below:

	Type of Area and Appropriate Level of Service
Highway Type	Rural Level	Rural Rolling	Rural Mountainous	Urban and Suburban
Freeway	B	B	C	C
Arterial	B	B	C	C
Collector	C	C	D	D
Local	D	D	D	D

Level of service = General Operating Condition

A = Free Flow

B = Reasonably Free Flow

C = Stable Flow

D = Approaching Unstable Flow

E = Forced or breakdown flow.

Relationship of Traffic to Highway Design

The major traffic elements that influence highway design are:

• Average Daily Traffic and Annual Average Daily Traffic
• Design Hour Volume
• Directional Distribution
• Percentage of Trucks
• Design Speed

Both ADT and AADT are fundamental measures of traffic flow. To the designer, most significant measure of traffic volume is the design hour volume, a two-way value, which may be determined by multiplying by AADT by a proportional representative of the amount of traffic occurring during the peak hour for an average weekday. This proportional value, known as the K- factor, typically decreases as AADT increases. The value of K ranges between 0.09 and 0.10 for many highways.

Foundation Engineering- Field Test

The reliability of Laboratory results to represent the in-situ soil properties remain significant concern to the Geo-technical engineer. The change in the environment conditions (e.g. pressure, moisture) and the disturbance that the soil sample under goes during extraction and subsequent handling and testing may greatly influenced the test data. Following tests are done for field test -

• Penetrometer Test
• Van Shear Test
• Load Test
• Observation Wells
• In-situ Permeability Test
• Pile Load Test

Geometric Design of Highways- Design Criteria

There are several criteria for geometric design of highways. These criteria or factor effects in designing of highways. The criteria or factors are given below:

• Design Controls and Criteria
• Roadway Capacity
• Design Speed
• Amount of traffic
• Design Vehicle

Geometric Design of Highway- Design Control and Criteria

The elements of designs are influenced by a wide variety of design controls, engineering, criteria and project-specific objectives. The factors are given below-

• Traffic Safety Consideration
• Functional Classification of the roadway
• Projected traffic volume and composition
• Require Design Speed
• Multimodal needs of the surrounding community
• Topography of the surrounding land
• Capital Costs for construction
• Agency funding mechanisms
• Human Sensory Capacities of roadway users
• Vehicle size and performance characteristics
• Public involvement, review and comment
• Environmental Considerations
• Right-of-way impacts and costs

Driver Perception And Reaction

Driver perception and reaction time is defined as the interval between seeing, feeling or hearing a traffic or highway situation and making an initial response to what has been perceived.

Perception reaction time varies from less than .5 sec to 3 sec or more. Green Shields has indicated that, in general:

1. The speed of all forms of reaction varies from one person to another and from time to time in the same person.

2. Reaction time changes gradually with age, very young and very old people being slower in their reactions.

3. People generally react more quickly to very strong stimuli than to weak ones.

4. Complicated situation takes longer to react to than simple ones

5. A person's physical condition affects his reactions. For example, fatigue tens to lengthen a person's reaction time.

6. Distraction increases the time of all reaction except the reflex.

Physical Properties of Waste

There are three physical properties of Solid Waste.

• Density
• Size Distribution
• Moisture Content

Density:
Density is the mass occupied by a unit volume of material. A high density waste capture system can reduce the volume in a solid waste management system, which substantially reduces the cost of :

• Collection
• Transportation
• Final disposal

Density Plays an important role in choosing the size and nature of collection vehicles.

Size Distribution:
Size distribution is important in designing collection vehicles and mechanical recovery systems, and in designing biological treatment methods.

Moisture Content:
Moisture content is defined as the ratio of the amount of water present to the total weight of waste material for a given waste stream.