Comparative Analysis of Mechanical and Manual Mode of Traffic Survey
Chapter One
AIM AND OBJECTIVES
The objectives of this research work are:-
- To determine the actual number of vehicles using the road, with an automatic recorder and at the same time counting manually to enable comparison between the mechanical means and manual counting.
- To estimate the present and projected future traffic volumes spanning 20 years using road traffic data obtained from the count.
- To determine the accuracy of data collected using different statistical methods.
CHAPTER TWO
LITERATURE REVIEW
TRAFFIC SURVEY/COUNT
- Traffic Survey may provide some precise information about numbers of vehicles, their type, weight or speed, but they cannot provide other data that are essential in transport planning, such as trip purpose, routing, duration etc. Collecting these data requires more extensive survey instruments (Slack, 1998). These instruments include:
- Mailed questionnaires: This can include a wide range of questions. It is relatively cheap to administer to large numbers of people, although preparation can be expensive; the main problem is the generally low response rate.
- Travel diaries: This involves soliciting respondents to keep a diary of the trips undertaken, times, purposes, modes etc. It is an extremely useful instrument but constrained largely by the number of people willing to complete such a detailed inventory.
- Telephone surveys: with automated dialing this can achieve extensive coverage, but response rates are usually low.
- Face-to-face home interviews: This can overcome many of the errors based on misunderstanding of questions in mail surveys, but are extremely time-consuming and costly.
The main problems encountered in traffic surveys are:
- Comparability between surveys. It is usually very important to compare survey results over time. This is frequently very difficult because of different sample sizes, different questions, different response rates, and different geographical collection units. These are usually major problems for studies trying to compare the results from different agencies.
- Non response bias. There are significant variations in the response rates achieved by surveys. The larger the non response rate, the less reliable will be the results. A 60% response rate is sometimes considered as a threshold. Many surveys fail to achieve high rates of response, for example the 2001 NHTS survey only achieved 41%.
- Coverage bias. The survey instruments frequently contain hidden biases. For example automatic telephone surveys exclude cell phone users and those without a land line connection.
- Unreporting of trips. Research is now showing that surveys and travel diaries may be undercounting trips made. Some test surveys are using GPS devices to record trips and indicate that in the Kansas City survey 10% of trips were unreported and in the case of LarEdor the figure was as high as 60% (Slack, 1998).
- There is a wide range of counting methods available. It is useful to distinguish between intrusive and non-intrusive The former include counting systems that involve placing sensors in or on the roadbed; the latter involve remote observational techniques. In general the intrusive methods are used most widely because of their relative ease of use and because they have been employed for decades. The only widely used non-intrusive method is manual counting, which enjoys wide application because of its ease. Intrusive methods, however, have evolved little over the last decade, but in the US, with federal transport policy emphasis on IT solutions to traffic management, progress is being made in the development of non-intrusive methods (Slack, 1998).
The major intrusive methods include:
- Bending plate: a weight pad attached to a metal plate embedded in the road to measure axle weight and speed. It is an expensive device and requires alteration to the road bed.
- Pneumatic road tube: a rubber tube that is placed across the lanes that uses pressure changes to record the number of axle movements in a counter placed on the side of the road. The drawback is that it has limited lane coverage, may become displaced, and can be dislodged by snow ploughs.
- Piezo-electric sensor: a device that is placed in a groove cut into the roadbed of the lane(s) being counted. This electronic counter can be used to measure weight and speed. Cutting into the roadbed can affect the integrity of the roadbed and decrease the life of the pavement.
- Inductive loop: a wire embedded in the road in a square formation that creates a magnetic field that relays the information to a counting device at the side of the road. This has a generally short life expectancy because it can be damaged by heavy vehicles, and is also prone to installation errors.
The major non-intrusive methods include:
- Manual observation: This is a very traditional method involving placing observers at specific locations to record vehicle or pedestrian movements. At its simplest, observers use tally sheets to record, but on the other hand there are mechanical and electronic counting boards available that the observer can punch in each time an event is observed. It can record traffic numbers, type and directions of travel. Manual counts give rise to safety concerns, either from the traffic itself or the neighborhoods where the counts are being undertaken.
- Passive and active infra-red: This uses a sensor that detects the presence, speed and type of vehicles by measuring infra-red energy radiating from the detection area. Typically the devices are mounted overhead on a bridge or pylon. The major limitation is the performance during inclement weather, and limited lane coverage.
- Passive magnetic: This uses magnetic sensors that count vehicle numbers, speed, and type and are placed under or on top of the roadbed. In operating conditions the sensors have difficulty differentiating between closely spaced vehicles.
- Microwave – Doppler / Radar: The mounted overhead devices record moving vehicles and speed. With the exception of radar, these device have difficulty in detecting closely spaced vehicles and do not detect stationary vehicles. They are not affected by weather.
- Ultrasonic and passive acoustic: These are devices that use sound waves or sound energy to detect vehicles. Those using ultrasound are placed overhead to record vehicle presence but can be affected by temperature and turbulence; the acoustic devices are placed alongside the road and can detect numbers and vehicle type.
- Video image detection: This makes use of overhead video cameras to record vehicle numbers, type and speed. Various software are available to analyze the video images. Weather may limit accuracy.
CHAPTER THREE
METHODOLOGHY
MATERIALS AND METHODS
The design of highway and its features is based on explicit consideration of the traffic Characteristics and volume to be served. Traffic volume affects the geometric features of design such as width, alignment, grades and so on.
DESCRIPTION OF STUDY LOCATION
The road Project traverses four (4) Local Government areas namely; Yala, Ogoja, Ikom, Etung and other important settlements in Cross River State. The road begins from Mbok which is located within 6º24’.00’’ North and 8º42’.00’’ East and ends at Ikom located within 5º58’.00’’ North, 8º42’.00’’ East.
CHAPTER FOUR
RESULTS AND DISCUSSION
The results of the field work and comparative analysis are presented in this section as Tables and Figures, for clarity and understanding.
CHAPTER FIVE
CONCLUSION AND RECOMMENDATION
CONCLUSION
In general, the following conclusions can be drawn from the study
- It was found that manual results compared fairly well with result obtained with mechanical device.
- The resultant effect of the ESAL value when wrongly computed has a downward effect on the structural thickness, such that cracks can appear at the earlier stage.
- The Mechanical method is more advantageous, less stressful, high accuracy compared to manual counter.
- Maintenance cost is high using mechanical counter compare to manual in terms of procurement, maintenance etc.
- Safety is better assured while using Mechanical Method when compared to the Manual counter.
- During raining season, the mechanical device cannot be put to use without protection.
- The graphs generated from the software show that traffic on lane 2 is impacting higher traffic load (See Appendices on volume report graph dated 2-26-15 respectively) in this case the traffic on lane 2 should be use for pavement design.
Nonetheless, the mechanical counter has better advantage compare to the manual counter and for this reason the mechanical counter should therefore be employed during the raw data traffic counter. Manual on the other hand was not very useful for traffic survey in predicting the future traffic analysis.
RECOMMENDATIONS
On the basis of the results of this study and taking into cognizance the implication of the above observations, the following suggestions are recommended for individuals, teachers, and government agencies as well.
- Based on the outcome of the study, the use of mechanical device is recommended for use in the traffic survey count, instead of the manual count.
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