The roadway where the traffic count was taken is listed first for each count location. As part of the description, the orientation of the location with respect to the nearest cross street or notable geographic detail is also listed. For example, "Rt 3A S of Bour/Plym TL" is shorthand for "Route 3A, south of the Bourne/Plymouth town line." Note that the counts performed on a town line are listed twice in the report. For each count location taken at a town line, the count location is given under both town names. This allows the data to be analyzed more effectively. See the complete listing of abbreviated terms in the Glossary of Abbreviations.
Under each location, all available counts are listed in reverse chronological order, with the most recent appearing first. The year, begin date and end date of a count are listed in the first three columns. Not all locations are counted every year, and some may be counted more than once in a given year. Generally, counts are conducted for a 48-hour period, although some cover longer periods. In order to monitor summer weekday traffic, most counts are conducted Monday through Friday during the summer season. When comparing counts taken in different years, it is important to consider fluctuations in seasonal visitation to the area as well as year-to-year growth. For example, a July 2006 count will generally be higher than an April 2007 count, mainly because of the seasonal visitation differences. Even the comparison of a count performed in July 2006 to June 2007 could be misleading due to the increase in traffic experienced during the month of July. However, if a count conducted in April 2007 shows an increase over a count performed in July 2006, for example, the effect may be a result of area growth. Seasonal adjustment factors can allow for a better comparison of data between different months.
Weather conditions may influence traffic volumes on Cape Cod. Cloudy days often contribute to increased traffic congestion except on beach access roads. On rainy or cloudy days, people engage in sightseeing or shopping rather than spending time at home or a favorite sunny-day location. In the data tables, brief descriptions of weather conditions during the count period are given. This information should be regarded with caution, as weather conditions may change considerably throughout a single day on Cape Cod. The Commission staff records the weather conditions of a count when setting down and picking up the traffic counting equipment. Of all the data provided in the tables, this category is the most subjective.
Direction identifies the direction of travel for the traffic on a roadway. Each traffic count is divided into three rows. The first row, "Total," lists the data for the sum of the two directions. The next two rows list the directional data, with the direction of travel for the row indicated by the Direction column. If the count was done on a one-way road, only data for the one direction are listed and are identical to the information listed in the Total column. If the traffic counter did not separate the counts into the directional movements, only the data for the summation of both directions are listed.
Speed limits are typically based on the 85th percentile traffic speed (the maximum speed at which 85% of the vehicles are traveling). The measured 85th percentile speed can be different than the existing speed limit because of factors such as changes in geometric roadway geometry and driver behavior. All new ATR devices can determine the speed of vehicle traffic. The Cape Cod Commission has begun to record this figure at the request of town, staff or MassDOT officials. The data are presented for each direction of traffic. Practical uses of the data could include evaluating the speed limit and safety of the roadway.
Average Daily Traffic (ADT) is an estimate of the average number of vehicles over a 24-hour period.
The Peak Hour is the highest one-hour traffic volume observed during the period counted. Three columns offer data on the Peak Hour of a count. The date and day of the week (Date&Day) in which the peak occurred is listed first. The hour of the day (Hour) representing the Peak Hour is listed in the second column using 24-hour time (e.g., "16" means that the Peak Hour occurred beginning at 4:00 p.m. and ending at 5:00 p.m.). The Peak Hour Volume (Vol) is listed in the third and right-most column. Please be aware that the two-way Peak Hour volume may not be equal to the sum of the two directional Peak Hour volumes. Instead, it may represent the hour within the period counted when the sum of traffic in both directions was greatest. Starting in 2011, peak hour volumes for each direction of travel correspond to the peak hour combined travel. This is to conform to MassDOT reporting requirements. Axle correction factors were used as necessary.
Peak Hour information is significant for transportation planning. First, it indicates the highest traffic demands on a roadway. Second, it can show how close a roadway’s use is to its capacity. For example, if counts taken in different years or during different months of the same year indicate a change in average daily traffic without a corresponding change in Peak Hour traffic, the roadway may be experiencing capacity constraints during peak times.
The "Four~Five" column indicates the average traffic volume recorded between 4:00-5:00 p.m. during the count period. As with the other categories of data, the 4:00-5:00 p.m. volume is given for the total of both directions first, and then for each corresponding direction. The two-way 4:00-5:00 p.m. average volume is equal to the sum of the two directional 4:00-5:00 p.m. average volumes.
The 4:00-5:00 p.m. volume has been included as an aid to transportation planners and engineers. In addition to these purposes, the 4:00-5:00 p.m. volume also provides useful information when compared to the Peak Hour volume for a particular location. For example, during the years 1984-2015, Cape-wide, the Peak Hour for the entire day generally fell between the hours of 4:00-5:00 p.m. (Rush Hour). The entire dataset supports this finding. It is still the case that the 4:00-5:00 p.m. volume is often the Peak Hour for the location.
The Annual Average Daily Traffic (AADT) is calculated by multiplying the ADT by a seasonal adjustment factor for the month of the count. MassDOT supplies these factors based on six permanent traffic-counting stations on Cape Cod. Note that this year-round AADT is only an estimate, based on seasonal changes in traffic volumes at these six locations.