> **Tram-trains for the Changing Metropolitans **

In US and around the world, there has been an increasing demand for a
seamless passenger rail system in large metropolitan areas. With aging
population, increased migration to these areas, traffic congestion, high
cost of gas and infrastructure, the need for an efficient rapid rail
transit system becomes increasingly clear. One innovation is a
shared-use light rail system or tram-train, which could provide
large-capacity rapid transit using existing rail infrastructures. Unlike
a new rail corridor that requires extensive land for its right-of-way,
this service can use existing rail network from downtown to the suburbs
and even to cities 50 miles or farther.  To hasten such systems, we need
a supportive public policy and detailed risk assessment method that will
demonstrate the true economic and environment benefits of this
innovative system compared with other modes of surface transportation,
such as highways and conventional commuter and rapid rail systems. 

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**Here is a tram-train alongside a high-speed train in Germany.**

**INTRODUCTION**

In August 2008, the U.S. Census Bureau released projections that the
United States will be more diverse racially and ethnically, and much
older, by mid-century. Minorities, now about a third of the population,
will exceed 50 percent in 2042, and will constitute 54 percent of the
population in 2050.   In 2030, when the baby boomers will be 65 years
old or older, nearly one in five U.S. residents will be 65 or older.
This age group will increase to 88.5 million in 2050, more than double
its 38.7 million in 2008. Similarly, those 85 years old and older will
more than triple, from 5.4 million to 19 million between 2008 and
2050.  By 2050, the minority population, that is everyone except
non-Hispanic, single-race whites, will constitute 235.7 million out of
the total population of 439 million.

At about the same time, the Transit Vision 2050 of the American Public
Transportation Association (APTA), projects that the 83 percent of the
U.S. population living in the top 100 metropolitan areas today will
increase to about 90 percent in 2030. Also, population has increased in
several parts of the United States and Canada showing the emergence of
very high population clustering, accompanied by integrated regional
labor markets, infrastructure, and cultural and land-use patterns. Just
as metropolitan regions grew from the cities of the 20th Century, the
mega-regions will take over that role in the 21st Century. While the
transportation vision of the second half of the 20th century
transportation was to build a network of high-speed interstate highways
to connect the nation, the first half of the 21st Century requires a new
transportation policy to make our metropolitan regions mobile,
efficient, economically strong, and connected with one another and with
heartland areas.

In a U.S. Department of Transportation (USDOT) program plan entitled
"Refocus. Reform. Renew.- A New Transportation Approach for
America"(Plan), also released in August, 2008, "*Reducing congestion in
major metropolitan areas"* is one of its primary objectives. The Plan
said that, according to the Brookings Institution, the 100 largest
metropolitan areas in the U.S. are home to 65% of the nation's
population and 68% of the nation's jobs, and generate 75% of the
country's economic output, and in 2005, 95% of the nation's trade moved
through these metro areas. Unfortunately, these same cities are
experiencing a growing crisis of congestion and metropolitan mobility.
According to the Texas Transportation Institute, on highways in major
U.S. metropolitan areas, between 1982 and 2005, hours of delay per
traveler nearly tripled and total delay and wasted fuel increased by
more than four-fold. Congestion not only limits mobility but also
impedes efforts to improve air quality and reduce transportation's share
of greenhouse gas emissions. Thus, it is clear that effective congestion
relief strategies must be pursued. It also said in part that targeted
incentives to use rail as an alternative mode to highway movement can
help to relieve congestion and lower the amount of highway maintenance.

Anticipating the needs of our metropolitan areas due to this coming
demographic change, the transportation community has searched for
innovative options over the last decade. Among all options studied, the
shared-use light rail or tram-train service has shown to be a seamless
passenger service suitable to meet the transportation need in emerging
metropolitan corridors without existing rapid rail services. This system
with light rail or diesel multiple unit(DMU) equipment could run on the
street as well as on mainline existing tracks used by conventional
freight and passenger trains (*1, 2, 3, 4*). . It could provide direct
rail links from suburban to downtown business districts. Two recent
research projects sponsored by the USDOT have shown the benefits of this
innovative rail service. Proposed demonstration projects, if funded,
could further prove its business viability.  

However, the current federal safety regulations, developed for
conventional rail equipment, would require a risk assessment using the
criteria of "equivalent safety", sometimes create an unfavorable burden
to any innovations.  Since the objective of the Plan is to reduce
congestion of our highways around the metropolitan areas, a
safety-and-benefit analysis should include all comparable ground
transportation systems to reach a valid and balanced comparison of true
benefits and safety.

This paper will summarize the present status of tram-train development
and proposed approaches. In the next section, it will describe the
tram-train here and abroad and the associated safety analysis method
being used today. Afterwards, it will propose an analysis method and
conclude with some recommendations.

**DEVELOPMENT OF TRAM-TRAINS**

Mixed use of light rail and conventional rail vehicles on common tracks
or corridors is not new in the United States. But it was discarded in
the 1960's along with numerous urban rail infrastructures. The modern
tram-train system begins with the conversion of the light rail system in
Karlsruhe, Germany, in 1992, on the Karlsruhe-Bretten-Gölhausen line,
with a total length of 30.2 km. (Figure 1). The success of the system
led to its extension to other lines around Karlsruhe.

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height="2.5131944444444443in"}

Figure 1 Tram-train of Karlsruhe, Germany

Several cities in Europe and the United States have found it
advantageous and irresistible to use light rail vehicles (Figures 2 and
3) or diesel tram-train (Figure 4) to extend rail service from city
center to suburbia via existing conventional railroad. This seamless
mode of transportation offers the most attractive and cost-effective
service to move large numbers of people through metropolitan areas
directly from homes to business centers without the need of transfer
stations, such as those between commuter rail and subway services.

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Figure 2 Tram-train of Saarbrucken, Germany

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height="2.285416666666667in"}

Figure 3 Tram-train of Salt Lake City

Using the rail network of French National Railways, the Saarbrucken
light rail system became the first international light rail operation.
As a result, more cross-border operations are being planned to integrate
the routes of four operators: Saarbahn, DB, SNCF, and Luxembourg
Railways. Other track sharing tram-train systems, which use diesel as
well as electric vehicles under various stages of operation and
planning, include those of Cologne and Kassel in Germany, Sunderland in
England, and small to mid-sized cities like Dueren, Germany which
utilized diesel vehicle technology. Similar tram-train services that
have been in place or planned for many other cities in Europe, Asia, and
the United States are part of a survey in a technical report on
Intelligent Transportation Systems (ITS) Technologies for Integrated
Rail Corridors that the Federal Railroad Administration (FRA) will
publish soon. The latest addition to those in service is the MetroRail
of Austin, Texas that will start operation in October this year. It will
employ DMU rail cars to serve downtown Austin that has not seen rail
service over a century.

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height="2.692361111111111in"}

Figure 4 Diesel Tram-train in River Line, New Jersey.

**SAFETY ASSESSMENTS**

The safety of tram-trains services in Europe is normally assured by
following national and regional regulations on railroads and street
cars. Such services may also be subjected to additional requirements for
vehicle design and operational control, such as speed, separation
distance, and braking performance.

In the U.S. the FRA, who has authority over all railroad safety issues,
has yet to establish the requirements for tram-train services, other
than a wavier process and a public policy statement jointly developed
with the Federal Transit Administration (FTA) which usually funds all
transit services in the metropolitan areas. All the existing or planned
tram-train services are using light rail or DMU vehicles that are
non-FRA-complaint equipment which means that they do not meet current
FRA safety regulations, particularly in its structural and glazing
strength requirements. Under the joint policy, details of proposed
plant, equipment, and operations must be submitted to the FRA in a
waiver request. To date, the FRA has only granted waivers for operations
where the passenger and freight services are subject to strict
time-of-day separation. As part of the wavier request, a safety
assessment is required to show the "equivalent safety" of the tram-train
service. Although no specific basic systems, or baseline safety criteria
is mentioned, it is assumed that any proposed new rail equipment should
be as safe as a similar service provided by a FRA-compliant or
conventional passenger rail equipment.

Based on previous safety assessments performed for some high-speed
trains and the Spanish Talgo train set, a typical safety analysis
approach was developed for non-compliant equipment (*6*). A similar
version of this method was also used to assess the safety of tram-train
services in a TRB/Transit Cooperative Research Project (TCRP), entitled,
Shared Use of Railroad Infrastructure with Non-compliant Public Transit
Rail Vehicles, for which a final report will be published early next
year. A simplified flow chart of such analysis is shown in Figure 5.

The results of safety assessment using this method with several
operational assumptions or options of a representative tram-train
service have shown that, given an adequate train control system,
simplified crash analysis, other reasonable risk mitigation measures,
and limited conventional freight services on the same track, such
tram-train operation could be as safe as a conventional passenger rail
service. When published, the aforementioned FRA and TCRP reports will
present details of the analysis and results, an established business
model, and some proposals for a tram-train demonstration project.

**Figure 5** Flow Chart for Safety Analysis of Non-FRA-compliant Rail
Equipment

**A NEW APPROACH FOR TRAM-TRAIN ASSESSMENT**

The proposed USDOT program plan "Refocus. Reform. Renew: A New
Transportation Approach for America," released in August, 2008, called
for a new approach for surface transportation. Among other things, it
called for a data- and technology-driven approach to safety to: (a)
strengthen the effectiveness and efficiency of Federal surface
transportation safety programs, (b) emphasize the importance of
risk-based, data and technology driven approaches that recognize the
diversity of safety challenges across the nation, (c) replace a variety
of narrowly-focused safety programs with an integrated safety grant
program that builds on the successes of the existing Strategic Highway
Safety Plans, and (d) encourage the use of crash-avoidance technologies.

The Plan also called for the use of benefit-cost analysis ("BCA") in the
selection of transportation projects with the highest return to each
dollar invested in our transportation systems. It aimed to help agencies
to organize and document their decision processes and to identify risks
and the most cost-effective means to mitigate them. Benefits typically
measured and monetized in BCA should include reductions in travel time
and vehicle operating costs as well as improved safety, reliability,
convenience, and passenger comfort.

The Plan noted that existing Federal transportation programs are
ill-suited to respond to the growing crisis of metropolitan
transportation congestion. Thus, many metropolitan areas have been slow
to adopt innovative transportation policies, technologies, and financial
arrangements. To this end, the Plan proposed a Metropolitan Mobility
(MM) program that would address these issues by providing substantial
amounts of performance-based transportation funding directly to
metropolitan areas with populations greater than 500,000. The Plan would
allow recipients broad multi-modal flexibility in selecting projects for
the movement of people and goods to reduce highway fatalities and
congestion with improved environment. The Plan also proposed a
performance-oriented pilot (POP) that would help innovative projects
like the tram-train.

In view of the new approach proposed to address the transportation
problems of metropolitan areas generated by the demographic transition
to an increasing aging population and a greater concentration of new
immigration internally and from abroad, an innovative system like the
tram-train service should be evaluated, not only by the "equivalent
safety" wavier process of FRA, but also by a BCA for its contribution to
the safety, congestion and environment benefits of the entire region.

Even the safety performance of such system should not only be compared
to that of an equivalent conventional rail service but to all other
surface transportation systems SERVING the same corridor because most of
the passengers who woould ride the tram-train would come from the
automobiles. Such a safety assessment approach was included in the
evaluation of the maglev system (*7*) by the USDOT to account the lives
saved as a result of diverting trips from highway to maglev service. In
addition, recent studies of the National Safety Council, as reported in
their 2005-2006 Injury Facts, showed that transit rail riders are 14
times safer than those traveling by car. Only by comparing the safety of
all surface transportation services, can a fair BCA be conducted.

**CONCLUDING REMARKS**

The great success of the tram-train concept has been reflected in a
large increase in the number of passengers. One of the main advantages
of the tram-train concept is the reduction of the door-to-door travel
time while making use of the older rail networks with advanced light
rail vehicles. Unlike the old street cars, the tram-train would provide
a truly integrated rail system to compete effectively with private cars,
but with less investment and with a lower impact on the environment than
a rapid rail system with completely new lines. In short, this type of
service offers a number of advantages such as:

Existing traditional railway infrastructure can be used, thereby
reducing the amount of investment necessary in new lines.

With additional stations, better equipment and shorter transient time,
more people will use the system.

With shared operations and crew, this system will be more efficient than
conventional systems, thus, it will reduce cost of operations and
equipment.

With direct access from the region to the main business and shopping
centers, it will help revitalize downtown areas and provide a better
quality of life for residents in general.

This service should help address the transportation problems of
metropolitan areas due to our aging population and greater concentration
of immigrants. To make this tram-train and similar innovative systems
viable, it should be evaluated, not only under FRA's "equivalent safety"
waiver process, but also under a benefit-cost analysis for its
contribution to the safety, congestion, and environmental benefits of
the entire region.

As our transportation infrastructure matures and demographic changes
accelerate toward more and larger metropolitan areas, it is clear that
tram-train services will be an attractive option. While the commingling
of different rail equipment is not new, it is crucial that
transportation planners are aware of this option and that they take a
proactive approach to regulations, physical plants, equipment,
procedures, and public policies to ensure excellent transportation
services for our nation.

To this end, a research project or pilot demonstration project with
detailed anaylsis and comparison of various acceptable criteria of the
safety assessment is recommended, in addition to the apparent
acceptability of "equivalent safety".

**REFERENCES**

1\. Tsai, T., Tram-Train: Mixed Use of Rail Corridors; Paper IMECE33252,
International Mechanical Engineering Congress and Exposition, New
Orleans, LA, November 2002

2\. Phraner, S.D. et al, Joint Operation of Light Rail Transit or Diesel
Multiple Unit Vehicles with Railroads, Transportation Research Board,
TCRP Report 52, 1999; and TRB Supplementing and updating TCRP Report
#52, June 2001

3\. "Germany's Track-Sharing Experience: Mixed use of rail corridors"
TCRP Research Results Digest 47, March 2002

4\. Novales, M., A. Orro and M. Bugarin, "The Tram-Train: A New Public
Transport System", TRB 81^st^ Annual Meeting, Washington, D.C. January
2002

5\. Resor, R., Catalog of "Common Use" Rail Corridors, Report
DOT/FRA/ORD-03/16, April 2003

6\. Bing, A., et al, Safety of Non-compliant Passenger Rail Vehicles,
APTA/TRB Joint Light Rail Transit Conference, St. Louis, MO, April, 2006

7\. The National Maglev Initiative, Final report, DOT/FRA/NMI-93/03,
September, 1993

***DRAFT 9/22/08***