Background[ edit ] On time performance is a measure of the ability of transport services to be on time. Almost all transportation systems have timetableswhich describe when vehicles are to arrive at scheduled stops. Transport services have a higher utility where services run on time, as anyone planning on making use of the service can align their activities with that of the transport system. On time performance is particularly important where services are infrequent, and people need to plan to meet services.
This glossary contains terms used when planning and designing samples, for surveys and other quantitative research methods. Abduction A useful but little-known concept first used by the philosopher Peirce around Similar to inductionit has been described as "testing a theory by fitting it over a framework of facts.
Adaptive sampling A method used for sampling rare populations. When you find something that you're Travel time reliability analysis in, you start to look more closely at nearby areas. For example, if you're studying a rare disease and find somebody who has it, you sample their neighbours as well.
This is often used in quality control - e.
Adaptive sampling is more efficient than random sampling, but calculating population estimates becomes more complex. Analysis Understanding something by dividing into smaller parts, and studying each part separately.
The opposite of analysis is synthesis. Survey analysis involves considering the responses to each survey question and pairs of questions. Axiom A statement that is so obvious that it's a starting point for any research.
For example, the laws of arithmetic are axioms. To say that something is axiomatic is to imply that it must be true. Sometimes axioms are revealed to be assumptions that are not always true. Birthday rule When a researcher contacts a household and says "I'd like to interview the person who last had a birthday" this is not an advertising gimmick, but a way of ensuring randomness - it assumes that people's birthdays are spread evenly across the year.
Census Survey of a whole population. Most countries have a Population Census with a capital C every 5 or 10 years, but a researched population can be much smaller. Thus a census with a small c of all staff of an organization would be a survey where everybody was sampled.
Their parents' permission is needed to interview them. Some countries have specific laws on this, and have higher age limits - up to Cluster When you are surveying people in their homes, it's very expensive to travel all around a city, interviewing at one home in each suburb.
For efficiency, most door-to-door surveys use cluster sampling, where a starting address is chosen at random, and interviewing is done at a number of nearby homes - often about 10 of them.
Convenience sample Using a sample of people who happen to be handy or easy to survey. May be OK in preliminary research, but not guaranteed to be representative of the population. Deduction Deduction is what you do when you know the principles of something, and deduce a particular case.
Induction is the opposite process. Dependent variable A statistical term for whatever measure you are trying to predict. See independent variable and regression. Dwelling The premises where a household lives. May be a house, flat, caravan, boat, etc.
It is a place, not a group of people. Effective sample size If you interview two people at the same household, and ask them a question they give the same answer to - such as "how many TV sets are in your home?
People in the same household tend to give identical answers, so in order not to waste interviews, it's often best to interview only one person per household. Empirical Based on actual data.
The opposite of empirical is theoretical. Error types Because a survey doesn't include all members of a population, or include all possible questions, various types of error can occur Type I error error of the first kind: Finding a result statistically significant when in fact it is not, i.
When a survey finds that a result is not significant, though in fact it is. Getting the right answer to the wrong problem. Not so easily quantified. Another way of looking at error types depends on the source of the error Coverage error - when the population sampled wasn't quite the population wanted.
Maybe a survey only included people who lived in the area, not visitors.This page provides travel time measures for the Strategic Road Network (motorways and ‘A’ roads managed by Highways England) and for locally managed ‘A’ roads in England.
If this analysis will account for changes in travel time reliability, then it will also be necessary to calculate changes in travel time variance and arrival delay (for example, the frequency of peak-period traveler arriving more than minutes later than average). Transportation Cost and Benefit Analysis II – Travel Time Costs Victoria Transport Policy Institute Travel Time and Reliability, University of Irvine (ph-vs.com); Travel Time Any time devoted to travel.
This is the least specific definition. The first of Gordon Woodcock's methods of interstellar travel is "go slow". Distance between stars is huge, traveling said distance slower-than-light will take a huge amount of time, human beings have a very limited lifespan. In addition, the Reliability Ratio is defined as the ratio of the value of travel time reliability, and the value of travel time savings.
This ratio permits estimation of the Value of Reliability, especially when only the Value of Travel Time Savings is known. Travel time reliability measures the extent of this unexpected delay. A formal definition for travel time reliability is: the consistency or dependability in travel times, as measured from day-to-day and/or across different times of the day.
Figure 2 further illustrates travel time reliability with data from a major commuter route in Seattle, Washington.