Editor's Note: The 266-mile bus network is a key feature of the enviable Stuttgart
public transit system, better known for its light rail components. This article discusses
the SSB integrated system approach to the bus network, which has helped win it
international recognition.
By Manfred Bonz
Chief Executive Officer
and Ulrich Weber
Stuttgarter Strassenbahnen
Stuttgart, Germany
An innovative bus acceleration program has shown how to make a bus system more
attractive in our city.
Stuttgart, the capital of the region Baden-Wrttemberg with a population of
550,000, is an international center of the automobile industry. The city and the whole
region is characterized by high car ownership- 560 cars per 1,000 inhabitants. This level,
comparable to the U.S., represents significant competition for the public transportation
system.
In recognition of this, the policy of Stuttgarter Strassenbahnen, the Stuttgart public
transport operator, has consistently been to offer high quality public transport. Besides
a modern 77-mile light rail and tramway network, SSB operates a 266-mile bus network that
carries some 170 million passengers annually.
While the expansion of light rail since the 1980s has helped to increase the
attractiveness of the Stuttgart rail network, the bus network became less and less
attractive. Delays longer than five to 10 minutes due to congested roads became a regular
occurrence on some of the SSB bus lines.
Since 1996, SSB, in cooperation with the city of Stuttgart, has developed a new program
to revitalize the bus network. The most significant city center bus line (Line 42) with
31,000 passengers daily was tackled first; other lines have followed. The innovative
measures on our "model" Line 42 obtained international recognition from the
International Union of Public Transport's Congress in 1997.
The "System Bus"
Similar to the light rail system, a new approach has been taken to consider the
different components of a bus network not separately, but as a whole system.
The vehicle, the route, and its stops, as well as bus operations, are brought into line
with each other.
Vehicles-Factors such as external design, attractive interior, and
ease of boarding determine the acceptance of buses. SSB has introduced articulated low
floor buses with a number of improvements on Line 42.
The low floor design ensures easier boarding and quicker spread-out of passengers in
the vehicles. This is supported by the kneeling mechanism and the vehicle's ramp. Comfort
has been improved by an air conditioned interior, as well as real time passenger
information inside and on the outside of the vehicle.
Route-The creation of 1.1 miles of bus lanes (8 percent of the whole
line length) has speeded up bus operations on Line 42 by enabling buses to run
independently of other traffic.
However, due to narrow roads and the hilly Stuttgart topography, varying from 207 to
549 meters in altitude, bus lanes could not be created to the same extent as in other
cities of similar size.
The design of bus stops also influences bus operation. To speed up boarding and
alighting, as well as to optimize filtering back into flowing traffic, 40 percent of all
stops along Line 42 have been upgraded and changed to bays that facilitate boarding and
reduce congestion.
The stops are equipped with higher curbs to allow buses to draw up close and parallel
to the curb. Boarding height could therefore be reduced to approximately 7 to 9 cm. In
combination with the vehicles' kneeling mechanism, this especially meets the needs of
older people, persons with disabilities, children, and mothers with carriages.
Operation-The most significant innovation on Line 42 has been priority
at traffic lights. Delays at traffic lights slow down bus operations, particularly in
inner city areas. On some lines, delays account for 15 to 20 percent of overall trip
times. Since bus lanes cannot often be created in heavily congested areas, "green
upon demand" meets not only the demands of a rapid bus operation, but also the
interests of other traffic participants.
In Stuttgart, even the traditionally conservative city council could be convinced of
the advantages of the radio beacon system, whereas other bus priority measures are always
difficult to realize.
The system operates with an infrared technique to detect the vehicle's location; a
Global Positioning System serves as a backup. A battery-powered infrared beacon
communicates with the infrared-vehicle-reading-system IRIS (Infrared-Information System)
of a passing bus. It tells after how many meters radio signals have to be transmitted from
the bus to the computer-controlled traffic light in order to get a green light. The system
records each bus for prioritization until the bus has passed the traffic light. This
barely interferes with other traffic.
Until now, 34 out of 38 traffic lights (90 percent) have been equipped with the radio
beacon system on our model Line 42. Considering the whole SSB bus network, 26 percent of
all traffic lights have been upgraded, giving buses priority over general traffic and
pedestrians.
Dynamic Passenger Information--Another innovation on Line 42 has been
the introduction of a dynamic passenger information system.
Data processors use the vehicle location system to calculate the time of arrival at a
stop. The real time is then displayed to the waiting passengers.
Results
The various measures called for an investment of $4 million, of which 85 percent was
met by public subsidies.
Optimal results have been achieved on Line 42, thanks to the implementation of a bundle
of measures involving simultaneous improvements to all components of the bus system.
Passengers have received a number of important advantages: more punctual departure and
arrival, reduced travel time, easier boarding, more comfortable buses, and better
passenger information.
From the operator's point of view, the increased travel speed from 9 to 10.1 miles per
hour had additional benefits. One bus per line could be reduced, for a savings of $250,000
annually.
Finally, the upgraded bus line has attracted up to 10 percent more passengers, showing
the success of the Stuttgart bus acceleration program. This is the only way for public
transport to reach its target: changing the modal split.
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