Field Operations Guide By: Elise Fisher Organization: EF Geographic. L.C. Response Time Analysis Brief Explanation: Uses GIS to assess expected response times from each of their existing public safety agency locations. From the results of this analysis, response personnel tasked with planning and maximizing resources can easily identify how different neighborhoods will be affected by changes in service levels. Public safety agencies can then make decisions about how to adjust staffing and equipment to maximize the effectiveness of available resources. This case study involves a Fire Department. Department Background: This example is based on Toledo, OH. Same methods can be applied to any size department. Size: Small Medium X Large GIS Ability: None In House X Consultant Data Needed: a. Fire Station preferably a GIS file, but an Excel, text, or dbase file will do with a little extra work. o Station Number Text o Physical Address - Text o ZIP - Text o Apparatus, including type - Text o Individual Apparatus staffing, including medic levels, if EMS calls will be modeled - Integer Street Network Routable Topologically correct o Necessary fields: Segment length - Double Speed - Integer o Optional Fields One Way based on direction of segment travel, populated with to-from (TF) and from-to (FT) indicators - Integer To-from elevation, populated with standardized values - Integer Fire Response Areas o Station Number, Text Alarm Configurations Software Required: ArcGIS (ArcView) Network Analyst Skills to perform tasks (i.e. Network Analysis, GIS Data editing, etc.): Assess GIS data and fields Open and close ArcGIS ArcView and ArcCatalog Add data into ArcView Assess data in ArcCatalog Create a Address Locator Geocode addresses. Ie., fire stations to street file, if necessary Import text data into geospatial format, if necessary Create and build a Street Network Create Service areas based on travel times using Network Analyst Modify and calculate in ArcGIS tables, if necessary Ability to label features in ArcView Symbolize data in ArcView Cartographically represent service areas and fire stations in an organized map.
Procedure: Prep the Street file for Network creation o Determine and verify units of length field, typically feet o Determine and verify units of speed, typically MPH o If using one-way segments, verify and/or create fields for one directional travels costs [TF_COST] AND [FT_COST] o Calculate travel cost, if your data contains one-way identifiers. Select: "ONE_WAY" = 'FT' If feet, Calculate: [FT_COST] = ((([Length]/5280)/ [MPH])*60), for length in feet If miles, Calculate: [FT_COST] = (([Length]/ [MPH])*60), for length in miles Non-FT values (all other records), Calculate: [TF_COST] = -1 Select: "ONE_WAY" = ' TF' If feet, Calculate: [TF_COST] = ((([Length]/5280)/ [MPH])*60), for length in feet If miles, Calculate: [TF_COST] = (([Length]/ [MPH])*60), for length in miles Non-TF values (all other records), Calculate: [FT_COST] = -1 Select all other records (two-way street segments), "ONE_WAY = '' If feet, Calculate: [FT_COST] = ((([Length]/5280)/ [MPH])*60), for length in feet If miles, Calculate: [FT_COST] = (([Length]/ [MPH])*60), for length in miles If feet, Calculate: [TF_COST] = ((([Length]/5280)/ [MPH])*60), for length in feet If miles, Calculate: [TF_COST] = (([Length]/ [MPH])*60), for length in miles. *At this point all values for TF_COST and FT_COST should have a value >0 or -1. There should be no 0s. Identify the elevation fields and not the meaning of the values. Close ArcView Open ArcCatalog Create a Street Network in ArcCatalog o Right-click on the streets file name, select New Network Dataset o Name the New Network Dataset something that makes sense to you, click Next o Make sure the connectivity is set to End Point, click Next o Use elevation fields if available, click Next o Select Yes and check the box for Global Turns, click Next o Change the Unknown Units of Cost units to Minutes o Highlight the Cost line, and click the Evaluators button. Make sure the newly created FT_COST and TF_COST fields are being used for the Values. Click Constant for Element Turn and select Global Turn Delay. Click the Evaluators Properties button. Uncheck the Only Show Turn Categories for Local Roads, click OK, click Apply, click OK, o Unknown Units for Oneway Name is ok. click Next, click Next, click Finish, click Yes to build the network. If fire stations do not currently exist in a GIS format, create a GIS layer by geocoding against the street file, from a text or Excel file. o Create an Address Locator from your street data. In ArcCatalog navigate to the directory where the street are stored (they should appear in the main window, not in the Table of Contents. Right-click in the main window and select New, Address Locator. If your fire station table contains ZIP Codes, select US Streets. If your fire station talbe does not contain ZIP Codes, select US Steets with Zone. Rename your Address Locator, Name: Navigate and Select your street file. Select all corresponding street fields.
o Click Tools, Geocoding, Address Locator Manager, click Add, navigate to your newly created Address Locator. o Open ArcView o Click Tools, Geocoding, Geocode Addreses, select your non-geographic Fire Station table, and select your Output shapefile or feature class: Click OK. o The Fire Station layer will appear in the Table of Contents. Symbolize the Fire Stations. The layer table with include all the attributes in your text or Excel file. staffing Create Service Areas o If you didn t need to geocode your fire station, add the geographic Fire Station GIS data and symbolize as you see fit. o Add in the new Street Network Dataset Select New Service Area from the Network Analyst menu. A new Service Area will appear in your Table of Contents. A Network Analyst Window will also show up to the right of the Table of Contents window. Set properties for the Network Service Area generation. Right-click Facilities in the Network Analyst Window to Load the Facilities in the Network Analyst Window. Select Load Locations. Select your Fire Station file from the pull down menu. Select the attributes you d like to view in the window for the Sort Field and the Property Name Field. Typically this is the station number. Click OK. The Fire Stations will appear in the window. Expand the + button next to the Facilities in the Network Analyst window, if the list doesn t expand and you d like to see the stations.
At this point you may start setting the properties for your Service Area. Right-click Service Area in the TOC and select Properties. Click on the General Tab rename the Service Area to something a little more useful. o Click on the Analysis tab and make sure your Impedance is set to Cost (Minutes). Enter the Service Area (travel time) you would like to create in the Default Breaks: window. Let s start with a 4 as the Default Breaks: value. Direction: should be set to Away from Facility. U-turns can be set at your discretion. Typically, they are set to Nowhere. Please make sure the Oneway box is checked. The Default Breaks: window controls the analysis measure (minutes) of the Service Area. It will be changed based on the desired analysis measure. Ie., 4-minutes, 8-minutes, 10-minutes of travel time. Click on the Polygon Generation tab. Un-check the Generate Polygons box. Click on the Line Generation tab. Check the Generate Lines and the Generate Measures boxes. Select Overlapping.
Click on the Accumulation tab and check the Cost box. Click on the Network Locations tab and verify the Facilities have been set to Location Type:. The rest of the defaults should work. Click OK. The Service Area properties menu will close. Solve the for the 4-minute travel time of all the fire stations. Click the Network Analyst Solve button or right-click the Service Area in the Table of Contents and select Solve. o The 4-minute Service Area lines will appear in the Table of Contents under your Service Area, Lines. At this point you should copy them to your computer. They are currently only temporary. Right-click Lines Data Export Data, select a directory, name and save. Repeat the steps above to calculate the 8-minute Service Area. Create 4 & 8-Minute Response area maps. 4-Minute Response Area
8-Minute Response Area *Warning some pre-constructed station locations may not be close enough to the street network to be routed. Moving the station locations closer to the street network (be very careful) allows them to be included in the routing. Additional Resources for performing Response Time Analysis Tutorial on modeling street networks GIS For Fire Station Locations and Response protocols, An ESRI Whitepaper