Department of Transportation

Mobility and Systems Engineering

Base Sat flow Rate
  1. To support the ongoing program of optimization and design of the traffic signals systems on the NJ State arterial network, the Bureau of Mobility Engineering (formerly known as Mobility and Systems Engineering) requires extensive evaluation and analysis of tasks to be performed as part of the design and development process.  These tasks follow the signal evaluation analysis, design and optimization procedures which are industry standards and are based on equations, coefficients, and other numeric values as recommended in the “Highway Capacity Manual or HCM”.
  2. The most fundamental and basic parameter for all signal analysis is the determination of the capacity of the intersections which is derived from the maximum vehicular volume that can flow through the intersection under ideal traffic and roadway conditions, also known as “Base Saturation Flow Rate” (BSFR).  The real capacity of the intersection is computed by adjusting the BSFR to the exiting roadway and traffic conditions based on actual field observation and data for each locations.  The BSFR is therefore extremely important in establishing the actual capacity and performance of the intersection.

  3. The determination of the maximum sustained vehicular volume through the intersection is a fairy complex parameter and requires extensive data collection and analysis.   This is generally beyond the scale of the average traffic studies which are limited in scope. Additionally the values established through individual traffic studies will require extensive statistical analysis and acceptance for becoming the “Standard Local Values”.  To overcome this issue HCM has proposed average “default” value of the BSRF which is generally used for analysis and evaluation purposes. However HCM strongly recommends establishing BSFR and other coefficients that are more accurate and realistic based on the actual local conditions. 
  4. After extensive research studies throughout the State, NJDOT, in collaboration with NJIT, have established BSRF values which are more reflective of the local conditions. Hence, these values are more realistic and accurate than the HCM default values.  For more accurate representation of the various characteristic influencing the vehicular flow, the State was divided into separate regions and BSFR values were determined for each region individually.
    A link to the study is provided here: study.

  5. The BSFR for each region are represented on the GIS map provided at this link: http://njdotintranet.njdot.lan/divbur/it/imtp/gis/geotrans.shtm

  6. Starting January 30, 2019, all traffic signal analysis or signal design work involving BSFR on State arterials will be required to use the BSFR represented on the GIS map.

  8. Step 1: Click on the link for the GIS map, provided above.
  9. Step 2: At the GEOTRANS page, select Transportation System Management, from the ‘Layer List’, provided on the top right corner.
  10. Step 3: under Transportation Systems Management, select, (a) BSFR Intersections at Regional Boundaries (b)BSFR Other Studied Intersections and (c) Base Saturation Flow Rate (BSFR) Regions.
  11. For difficulty of accessing the map or the study please contact Felipe Hernandez

The following manual/guidelines have been identified as documents that possibly use BSFR in their calculations, and may have some impact on the way analyses are performed:

a. Road User Cost Manual , (Capital Program Support, Value Engineering Unit)

b. TSM Procedures Manual (Mobility Engineering)

If you have any questions about Saturation Flow Rates and the decision to utilize the new values, please contact Rich Casmer.

Last updated date: September 12, 2023 9:51 AM