A way to reduce CO2 emission and traffic congestion in San Francisco

Kombo provides the foundation for true multi-modal, flexible and green transit in San Francisco


In order to meet the challenges of transportation in San Francisco, we present a proposal that introduces a new mode of public transport while also allowing for improved utilization of the existing transportation service infrastructure by combining different modes of transport. This requires creating a service management/integration platform to serve as a foundation for true multi-modal transportation. We call this platform Kombo.

Kombo is a platform for San Francisco’s citizens to improve their end-to-end trip options and the quality of their local travel. In order to deliver more customer-focused service, a new public transport tactic is needed: flexible transit. Flexible transit represents the “filler” that eliminates gaps in the current public transportation services. With flexible transit as an option, Kombo is better able to function as a glue that combines the other transportation services that SF has to offer.

In some areas, flexible transit will augment the existing public infrastructure and private offerings – i.e., it will fill in the gaps. In other areas, flexible transit will be a cost-effective alternative to fixed lines, especially in areas where demand and/or supply vary widely throughout the day.

The concept advanced here is the merger of two known and proven solutions: a flexible transit solution operational in several US cities and a national flexible transit platform for the country of Denmark. Our vision is to bring the logic of these two proven operations/technology platforms together in order to create an innovative solution for travelers throughout San Francisco.

Want to know more?

We really appreciate your time reviewing this website. If you like to know even more, click the button below to download our presentation on the Kombo Platform.

The Kombo Concept

The suggested concept consists of two parts. The first is to establish a prototype setup of flexible transit in a relevant area of San Francisco. The second is creating a publicly available and open data-service, which will support the combination of flexible transit with all other transit options offered through open data-services as well.

The result will be a platform for building customer apps which provides a one-stop experience, as well as partnering with other parties such as Google Maps, Apple Maps or RideScout. Such a platform could also support a variety of third party vendors which can use these publicly available data to create unique experiences for travelers, as well as integration with private transport providers, such as Lyft, Uber, etc.

Flexible Transit Explained

Flexible transit solutions serves trips in direct response to passenger demands for origin to destination service, traditionally served address to address, allowing travelers to share rides on-demand. Flexible transit comes in many varieties which can be utilized in different situations:

  • Demand Responsive Transit (DRT) provides dynamic on demand address to address service, which  can be either immediate (ASAP) or reserved in advance
  • Checkpoint DRT provides service from point to point with multitude of points in service area, passengers must walk to/from checkpoints to access the vehicle
  • FlexRoute is when a route has origin and terminus and usually one or more intermediate stops, but the vehicle will dynamically deviate from the route on demand to pickup or drop off passengers

It is important to see flexible transit solutions as a manner of transporting smaller groups of travelers compared to well-patronized fixed route services, and to have a much smaller capacity. DRT and other flexible transit services starts to have better advantages as population and trip densities decrease, and also tend to be much less expensive to produce and operate compared to conventional fixed route services. The target markets of flexible transit are segments of all the general public transportation markets—work trips, shopping trips, social-recreational trips, trips to health care, etc. 

Flexible transit are thus more tailored to individual trips, including seniors, those with minor mobility limitations, riders carrying packages etc,. compared to conventional fixed route transit options. This is done without the cost usually attributed to such services, as different types of transport can be introduced to provide the necessary capacity for the task or area.

Flexible Transit in San Francisco

San Francisco’s public transport system offers a high level of service by fixed route transit in many parts of city and for many people. Transit trips in the SF area represent 31% of non-walking trips in SF (SFMTA 2014 survey), and 63% of the trips are made by private auto. This gives a large room for growth in public transit usage. As in all cities, many local trips are not conveniently made by the current transit system given its radial focus and concentration of service in the central region of the city. Fixed route service cannot easily serve all of the diverse trip making needs of local residents.

Flexible transit will be focused on under-served markets. Particularly in the western and southern areas of city with less dense transit service compared to the central region, short and medium trips may not be well served by fixed route service. Many trip’s origins or destinations don’t closely follow the routes of transit lines, resulting in significant walk distance to transit stops— both are deterrents to use the conventional transport options. Flexible transit brings the public transportation service more closely to the rider, creating an opportunity to provide quality service to residents in such situations.


The core of the platform is an automated vehicle scheduling system that determines which vehicle in a service zone to assign each customer trip to as well as the sequencing of passenger pick-ups and drop-offs and the routing of the vehicle. The scheduling system must handle a multiplicity of service configurations, ranging from many-to-many “classic” DRT services in some zones to more structured services in other zones—such as feeder services to light rail stations and services with checkpoints or flex-routes—and both one-time and subscription trips for passengers. DemandTrans’ MobilityDR system, a precursor of the Kombo platform, incorporates multiple scheduling algorithms, used as appropriate, to enable these locally-tailored services to operate effectively.

By combining datasets (e.g., GTFS data) from other public transit services, the platform can function as a first-mile or last-mile feeder service to SFMTA Metro and BART stations, which is another prime market for flexible transit. The long walking distances to rail stations confronting some residents represent another deterrent to high levels of transit use. By using GTFS real-time data to “coordinate” itself with rail transit or express bus services, the Kombo platform enables flexible transit to become a high quality access mode that not only can overcome these distance hurdles by delivering users directly to rail transit stations, but by delivering passengers just in time to make a convenient inter-modal connection.

Environmental Impact

The Kombo platform will facilitate the development and growth of flexible transit in San Francisco. Moreover, various studies suggest that as many as 40% of the users of flexible transit will be replacing automobile trips. If Kombo can attract 5000 trips per day by the beginning of Year 2, as appears to be feasible based on ridership generation in Denver for similar services (adjusting for the differences in transit market penetration between Denver and San Francisco), and the average trip length is 2.5 miles (comparable to Denver users of flexible transit), it would reduce automobile VMT by 1.66 million miles annually. This would result in a reduction of 754 tons of CO2 annually, plus smaller amounts of related greenhouse gases. 

By the end of Year 2, when ridership handled via Kombo is estimated to grow to as much as 15,000 trips per day, the 6000 daily automobile trips that would be eliminated represent an annual VMT reduction of 5 million miles, equivalent to removing 2250 tons of CO2 emissions annually.

Meet the Kombo-team

The team behind the Kombo concept has many years of combined experience in both the practical and theoretical aspects of  combining and optimizing the different modes of transport, making it possible to reduce both cost and CO2-emissions without reducing the level of service for the citizens of San Francisco.

Roger Teal

President, DemandTrans Solutions

Dr. Teal is a former tenured faculty member (Civil Engineering) at the University of California, Irvine with more than 35 years of research, consulting, system design, and technology development experience in the area of flexible transit. He has worked closely with the Denver transit agency in helping devise their many flexible transit services and in ensuring that DemandTrans’ MobilityDR technology platform—which he designed--could handle their needs. Dr. Teal has 20 years of experience in directing the development of large software applications implemented by his company for a variety of clients.

Todd Voirol

Software Designer & Engineer, DemandTrans Solutions

Todd Voirol is a senior software designer and engineer for DemandTrans Solutions, and is the main architect of the MobilityDR platform which is used by the Denver RTD, Salem-Keizer Transit, Pace in Chicago and AC Transit for their flexible transit operations. Todd specializes in designing and implementing SOA systems across a wide variety of platforms, and has developed mission critical systems for over 15 years.

Niels Tvilling

Management Consultant & Flexible Transit Specialist

Niels Tvilling has 20 years of experience in the field of flexible transit in Denmark, both in terms of implementation, operation and the continued development, and is the chief architect behind Denmark’s national flexible transit platform. Niels Tvilling has also spent 10 years on the city council in the fourth largest city of Denmark, Aalborg, making him very comfortable working within both the constraints and possibilities of public office.

Tom Williams

Public Transportation Planning, Wight & Co.

Mr. Williams has 35 years of experience in transportation projects including rapid transit, BRT, commuter rail, LRT, Streetcar, and heavy-haul freight rail. Projects have included planning, operating plans, maintenance facilities and yards, risk management, and value analysis. His background is particularly suited to projects requiring innovative solutions and integration of complex systems.

Charlotte Frei

Flexible Transportation Planning, Wight & Co.

Dr. Frei is a Transportation Planning Engineer with expertise in design of flexible transit, including the operational and behavioral challenges associated with the delivery of these modes. Her dissertation simulated services and trade-offs associated with introducing checkpoint stops into existing service areas to evaluate trade-offs in equity, efficiency, and reliability. Findings indicate checkpoints reduce travel distances (hence emissions) and improve reliability for users while permitting enough flexibility for customers who require ADA-complementary service.

Projected Timeline & Milestones