The vast majority of projects are technically evaluated.
Some projects such as an animal control facility, a fire station or a sheriff’s substation are so unique in purpose or service that the county only takes on such projects on a very intermittent basis. These projects literally have no competition. The public service derived from one of these types of projects is so unique and necessary that they are singular in nature for the purposes of a technical evaluation.
On the other hand, road projects which are planned and built on an ongoing basis, have numerous requests that must each be technically evaluated.
Projects are ranked among others of their type because they share a common public service. All roads provide mobility and safety so they are compared and ranked against one another. Drainage projects remove structures from the flood plain. There is no way to determine if the public service from a road is better than that derived from a flood control ditch. They provide different and distinct public good.
Comparing them to each other is akin to comparing 'apples' to 'oranges'.
The numerical number is a measurement of the public service provided by a project and is used as the primary ranking tool.
The letter is indicative of other attributes directly related to the project and is only used as the tie breaker between projects.
Lower ranked projects might be selected because it is likely that they can be completed within the context of the two year bond cycle. While a higher ranked, longer term project might be put on hold until other funding sources become available.
Project readiness, or a project having completed design plans, is another factor that might determine if a lower ranked project is selected.
Project requests can be made at any time. Generally, the closing date for submitting a project request for a bond cycle is mid-May of the bond year.
Basic roadway features in the network database comes from the County Public Works Division, which maintains a GIS inventory of county roads. It is combined with road centerline features that are maintained by other sister agencies in the region, such as the City of Albuquerque and the Mid Region Council of Governments. The roadway network used here is a comprehensive coverage, including all local streets. In fact, this database also includes network information for other modes as well, including sidewalks, bike lanes, trails, etc. for analyses that involve non-motorized travel.
Almost. A standard street centerline file can be used as a network database provided travel speeds have been assigned to roadway links through some mechanism. Also, the model actually requires the database to be compiled in a way that makes it easy for the application to used – however, TRAM provides a mechanism to do this automatically. As a practical matter, we place a lot of care in the preparation of the network database so it is maintained as an important database for the region.
Posted speeds on major highways are available from the region’s travel demand modeling network. Congested speeds for major roadways (functional classes “collector” and above) typically come from the region’s travel time database that is created and maintained by the MPO. Average AM and PM peak hour speeds are available from travel time surveys. Speeds on other roadways, for example local streets, are typically estimated based on presumed speed limits (for example, 15 mph or 20 mph).
The model can use any zone-based source of information depicting the location of population and employment. Here, the socioeconomic database for traffic analysis zones created and maintained by the MPO is typically used. It contains information on current population, households, jobs, etc. This database is periodically updated to a new base year by the MPO. The current “base year” that is available in this region is 2010, coinciding with the census.
One of the things that TRAM does when converting a straight roadway centerline file to a TRAM network database is to represent directions of traffic flow explicitly. So a 2-way roadway is represented as two coincident opposing directional features, each with its own speeds (in the peak direction and in the off-peak direction). This means that the travel time contours generated by the model accurately capture travel in the peak and off-peak directions.
Yes, the model can use any source of demographic information that is associated with a zone system (GIS polygon features). The user can identify the source that should be used for an analysis.
The TRAM model automatically apportions values associated with a zone to the area within a contour by assuming that population in the zone is uniformly distributed throughout the zone. This is to say, it creates its estimate by prorating population on the basis of area.