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Demand Response Data Access & Communications Choices

Thank you to guest blogger Steve Yaffe for writing this blog on factors that influence our decision when procuring technology for scheduling and dispatch for transit agencies. This blog is a continuation of the Technology for Demand Response Transportation series.

This blog delves into choices we face when procuring technology for scheduling and dispatch. Key issues in making these choices are:

  • Dependability (no communications = major challenges providing service)
  • Data Security
    • Personal Information needs protection from hacking
    • The privacy of health-related information is protected by HIPAA and several state laws
    • Hackers could upload malware and hold data hostage for ransom
    • Financial security if customers can prepay fares
  • Cost

1. Data Storage

Older demand-response scheduling software was designed to operate on in-house servers. The agency would need an air-conditioned carpet-less room with a waterless fire protection system, a backup energy source if the power goes down, plenty of electrical outlets, a T-1 fiber-optic line capable of carry data at a rate of 1.544 megabits per second to a web server¹, and a rack to hold servers.  Besides the web server, a separate server may be required for the client, vehicle, and other database, another server to handle batch scheduling, and a fourth server for digitized Voice Over Internet Protocol (VOIP) communications.

The alternative is to place and access data and communications on the Cloud.  Some demand response scheduling software vendors have arrangements with cloud computing vendors such as Amazon Web Services, Microsoft Azure, IBM Cloud, etc.  These companies operate massive data centers.  Customers are enabled to connect to their databases via the internet – no need for a T-1 line or most of those servers.

Several factors are moving the industry towards the Cloud.

  • The cloud providers must deliver secure infrastructure to stay in business. They provide “private cloud” service for this purpose, with Identity and Access Management protocols to restrict viewing and data manipulation on an individual need-to-know basis. The database administrator functionalities on the older server-based systems still exist on the cloud.
  • The size of the databases are easy to scale on the Cloud. Databases can grow with the number of clients, rides provided and service area.
  • Cloud service providers are able to invest more than a typical enterprise (especially public sector) for functionality and security.
  • Due to their larger scale operations, Cloud service providers can attract the best talent. Amazon Web services, for example, has its own cryptography team.
  • Cloud service providers pay for the energy consumed and consequently have an economic incentive to reduce energy consumption, use energy more efficiently and create or underwrite new power sources.
  • Cloud service providers also have an incentive to maximize the speed of data transmission while minimizing the energy requirements of that transmission.
  • Our industry is moving towards real-time dispatching to maximize use of the vehicles. Manifests might be printed as a back-up, but not distributed.  Drivers will get their pickup and drop-off stops dispatched real-time.  Accessing and distributing information via internet is key to this functionality.  Cloud services are incented and have the resources to effectively use 4G and prepare for 5G (fifth generation wireless technology for digital cellular networks) functionality as the internet matures. These improvements will enable more data to be transmitted in less time than now.

2. Data Communications Venue

I’m aware of two venues for communicating with vehicles: cellular and FM radio.  Satellite would be a third, except for the expense.  Cellular has a clear advantage in urbanized areas, with plenty of coverage and repeaters to handle urban canyon and other spots that would otherwise not have reception.  Urban cellular coverage and processing speeds are improving.  Cellular also requires minimal equipment on the vehicle – just a tablet or a cell phone.

In rural areas, cellular reception (and cell towers) tends to be along major roadways. The further away from the roadway, less cellular reception.  Some carriers have better coverage in rural areas than others (AT&T, U.S. Cellular and Verizon, particularly) – but the dead spots in much of rural America are huge.  Several ideas have been  floated to improve rural coverage (including using high-altitude balloons), but none have been funded.

The alternative for rural transit is to use an FM channel in the 30-1000 MHz range.  Companies using FM for dispatch can rent one frequency or two.  If they only use one frequency, then voice communications will always take precedence over data transmissions. Using two frequencies allows uninterrupted transmission of data.  Vehicles would need a separate antenna, connected to an on-board router.

FM signals can be received up to 100 miles away, depending on topography and the power to the transmitter.  FM works better in a relatively flat area – or if the radio tower is atop a volcano (the range increases with tower height).  Quadrupling the power of the transmitter will double the range of the transmission². The data rate will be about 4600bps.

Cellular transmissions have similar challenges – power and height are also helpful. In ideal conditions – flat terrain, few buildings, signals can reach as far as 45 miles for voice communications – but 22 miles is likely the limit for uninterrupted data communications now³. As 4G and 5G become more prevalent, more towers are needed, though at lower power.

Another difference is the communications.  Cellular is on a 1-1 basis (dispatch <-> vehicle) while FM is normally 1-Many (Dispatch-Fleet) but can also be 1-1 (vehicle-dispatch) or Few-Few – FM talkgroups are configurable.  FM can handle text messaging as well as data (GPS, for example) and voice communications.  Technology has progressed to the point that a TDMA FM channel can poll 1,000 terminals (Dispatch, Maintenance & Revenue Fleet radios) per minute at a 9.6 kbps gross bit rate.  Two-Way data communication requires a DMR III control trunking channel with a YK channel designator to keep the channel clear of other users.

For those who intend to investigate the availability and appropriateness of FM, the first question is whether a frequency is available.  The first stop should be The Enterprise Wireless Alliance (EWA). EWA is a national association for the land mobile radio industry and also a frequency coordinating agency.  Customers would want a repeater pair of frequencies –  perhaps two or three pairs to cover a large area to include an exclusive use designation YG.  Agencies could use VHF or UHF as long as they are repeater pairs.  To learn about the technical standards for this technology, contact the Digital Mobile Radio Association.





Your comments to these blogs are welcome – please email the author at

Steve Yaffe is an independent consultant and a contractor for the National Aging and Disability Transportation Center.  He draws upon 40 years’ experience planning, procuring, overseeing and evaluating demand response and fixed route transit services, including 16 years with a consolidated human service transportation program.  He has served on research panels and co-chaired the 2019 Transportation Research Board’s International Conference on Demand Responsive and Innovative Transportation Services.

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