Lab 4 - Building Networks

Lab 4 was a bit of review for the exercises I have done building networks in my past courses, however this time we looked at more attribute details. We watched a series of short ESRI videos that discussed adding restrictions, working with evaluators, and other values that can be added to a network to create a more cost specific route.

The lab assignment consisted of completing a few tutorials on building networks with the Network Analyst in ArcMap, then exercises to practice what I learned. The first network I created was fairly simple, using provided San Diego street and facilities data to create a route with 19 stops. No traffic data was included in this first route. Analysis settings were based on minutes as the impedance, allowing the reordering of stops outside of the first and last, and only one-way turns were restricted, with meters and minutes calculated along the way. For this route, the total travel time was 97 min and the total distance was 94.7 km, although again, it is not based on any specific travel time or traffic data, just strictly the distance of each road segment and time based on distance to travel those road segments.

The second network I built included more traffic and travel time functionality. Using historical traffic data tables, one showing the speed factor profiles for each street segment during 15 min intervals over a 24 hr period and the other showing weekly travel times for each street segment based on the profiles, the network now reflected travel times over different times and days of the week. The Analysis settings were the same as before, except this time I selected a specific time and date for the route . I chose 5 pm on a Monday. The total travel time was 98 min and the total distance was 95.3 km.

While there were no required deliverables of the map, I am including two screenshots to show some of the variation in routing that occurred between the two networks. Also, as I lived in San Diego for a few years, I experimented with a variety of days and times just to look at route variation based on what I know of the traffic in the area. The most noticeable difference in all dates and times I chose was around Interstate 805 were it heads toward the Mexican border crossing, and you can see some variation there in the second screenshot between stops 13 and 14. While I haven't cared for working with network datasets much in the past, I enjoyed delving into the historical traffic data tables and details of evaluators in the network to expand my understanding of how traffic reflective routes are created.

Route created from a network with no historical traffic data included. This route reflects 19 stops at along a route in San Diego. Travel time: 97 min, 94.7 km

Route created from a network using historical traffic data. This route reflects 19 stops at 5 PM on a Monday in San Diego. Travel time: 98 min, travel distance: 95.3 km.