Discussion Board Essay Example | Topics and Well Written Essays - 750 words - 1

Discussion Board - Essay Example Conversely, "passive" ITS probe vehicles are vehicles that are already in the traffic stream for purposes other than data collection. passenger in the test vehicle; Historically, the manual method has been the most commonly used travel time data collection technique. This method requires a driver and a passenger to be in the test vehicle. The driver operates the test vehicle while the passenger records time information at predefined checkpoints to the transmission of the test vehicle; Technology has automated the manual method with the use of an electronic DMI. The DMI is connected to a portable computer in the test vehicle and receives pulses at given intervals from the transmission of the vehicle. Distance and speed information are then determined from these pulses satellites. GPS has become the most recent technology to be used for travel time data collection. A GPS receiver is connected to a portable computer and collects the latitude and longitude information that enables tracking of the test vehicle. Each of these test vehicle techniques is described in detail in the following sections of this chapter. The following elements are included for each technique: overview, advantages and disadvantages, cost and equipment requirements, data collection instructions, data reduction and quality control, and previous experiences. Since the driver of the test vehicle is a member of the data collection team, driving styles and behavior can be controlled to match desired driving behavior. The following are three common test vehicle driving styles (1): - Average car - test vehicle travels according to the driver's judgement of the average speed of the traffic stream; - Floating car - driver "floats" with the traffic by attempting to safely pass as many vehicles as pass the test vehicle; and - Maximum car - test vehicle is driven at the posted speed limit unless impeded by actual traffic conditions or safety considerations. The floating car driving style is the most commonly referenced. In practice, however, drivers will likely adopt a hybrid of the floating car and average car because of the inherent difficulties of keeping track of passed and passing vehicles in high traffic volume conditions Advantages and Disadvantages The manual method (pen and paper) has the following advantages: - No special equipment needs; - Low skill level (no special hardware training); and - Minimal equipment costs. The manual method (pen and paper) has the following disadvantages: - High labor requirements (driver and observer); - Low level of detail (average speeds for 0.4 to 0.8 km, or 0.25 to 0.5 mi). Average speed and delay are reasonable while queue length and speed profiles are difficult; - Greater potential for human error (potential for marking wrong checkpoints or inaccurate times); - Potential data entry errors (e.g.,