|Japan Railway & Transport Review No. 51 (pp.28–39)
Feature: Railways and The Environment(part 3)
Development of Dual Mode Vehicle and its Effects
This year marks the twenty-second year since the Japanese
National Railways (JNR) privatization and breakup, resulting
in the establishment of JR Hokkaido. JR Hokkaido currently
operates approximately 2500 km of track, of which a third—
about 800 km—has less than 500 passengers a day per km
(dotted lines in Figure 1). Passenger levels on these rural
lines have continued to decline year-by-year with business
conditions becoming severe and running at a loss, as is
also the case with local bus services. The reasons include
depopulation of rural areas due to declining birth rate and
aging population, a critical situation for local bus businesses
following deregulation and fewer government subsidies,
and a greater ratio of households with private automobiles,
although the public still wants public transportation. In
response to this situation, JR Hokkaido has implemented
management reforms for rural transport lines, substituting
buses for some, running one-man trains, re-examining
branch office business, re-examining station business, and
making other changes to support continued operations.
Overall DMV System
The JR Hokkaido DMV is a modified microbus that runs on
both roads and rails. Attempts to build such a vehicle have
been a transport dream for about 75 years. The system
as a whole is composed of the DMV vehicle operating on
roads and rails, the mode interchange system for changing
between road and rail quickly, and the traffic control system
managing DMV operation. Development of the overall system
is ongoing at the Dual mode Transport System (DTS). Details
of subsystems are described below.
|Figure 1: JR Hokkaido Current Passenger Densities
Photo: DMV911/912 driving on road
Photo: DMV911/912 running on rail
Figure 2: Mode Interchange System
Photo: Mode interchange (Hamakoshimizu Station)
A DMV travels on roads using rubber tyres just like a normal
bus, and on tracks it travels using guide wheels mounted
on the front and rear of the body and rear rubber tyre
drive wheels (inner wheels). Switching from road to track
is done by entering the tracks along the guideway of the
mode interchange composed of guideway, rails, and paved
surface. At the interchange, the front and rear guide wheels
are lowered hydraulically and the front rubber wheels are
raised. When switching from track to road, the front rubber
tyre wheels are lowered and the front and rear guide wheels
are retracted into the car body to complete the switch in
approximately 10 seconds.
|Figure 3: Cross Section of Mode Interchange|
|Smooth and certain mode change must be possible
even when rails, guideway, tyres, and parts are not exactly
at specified dimensions. Therefore, the wayside mode
interchange part gauge was widened 70 mm to 1137 mm and
the guide wheel rim width on the vehicle was widened 25 mm
to 150 mm.
The second measure was lengthening the lifespan of rubber tyres. The rear rubber tyre drive wheels and rear guide wheels are located close to each other, so the load of the rear car body is distributed between these wheels. However, the drive performance of the rear rubber tyre drive wheels and rail tracking ability of the rear guide wheel drop with such placement. Furthermore, the contact width of the rear rubber tyre drive wheels when on rails is about 30% that on the road, placing an extra burden on the tyres. To achieve both drive performance and rail tracking ability, a rear axle load distribution control system (variable axle load control) is under development (Figure 4). This system determines the load status and conditions such as rear tyre slip, and maintains the optimum drive force for the rear rubber tyre drive wheels while placing the rest of the load on the rear steel wheels. This reduces wear on the rear rubber tyres and helps prevent derailment of rear steel wheels.
The third measure is improved stable running. In addition to the rear axle load distribution control system, improvements have been made to the soft suspension of the axle box and guide wheel tread shape.
Concerning soft suspension, the DMV wheelbase is about 6 m longer than railway rolling stock and the lateral force on guide wheels travelling through curves is large in relation to the wheel load, increasing the risk of derailment. To reduce lateral force, the guide wheel axle box suspension is soft supported by a tubular rubber spring and the guide wheel is steered by lateral force when travelling through curves. Figure 5 shows the axle box soft-suspension system. For the guide wheel tread shape, the load of the body back end is distributed between the rear rubber tyre drive wheels and rear guide wheels. Therefore, there is insufficient load on the rear guide wheels, increasing the risk of derailment. To relieve the insufficient axle load, the flange angle of the guide wheels has been increased to 87°, much more than conventional rolling stock, and the flange height is 33 mm (Figure 6), giving a derailment quotient of 2.33.
An additional fourth measure is the traffic control system described later.
Since the completion of the DMV test vehicle in January 2004, many people have observed and made test rides. One request was to increase passenger capacity. The microbus has a smaller allowable load than the DMV test vehicle, so it was difficult to secure a capacity equivalent to the test vehicle. As a result, efforts were made to increase transport capacity by coupled operation as shown in the two photographs. Forward-direction coupling has two vehicles connected in the same direction. This method has the benefit of using the drive power of both vehicles, and acceleration, braking, and other operations of the front and back car are synchronized. Actions such as opening and closing passenger doors can be synchronized too.
Reverse-direction coupling has driver’s seats at the front and back, giving the benefit of moving easily between cabs when operating only on tracks. However, damage to transmission and other parts can happen to automobiles running in reverse at high speeds over long distances, so a disconnecting device that cuts the power transmission at the rear car, allowing operation as a trailer, has been trialled although the long-term effects of reverse wheel rotation need further verification.
|Figure 4: Rear-axle Load Distribution Control System (Variable Axle Load Control)
Figure 5: Soft Suspension System
Figure 6: Steel Wheel (Guide Wheel) Profile
|The DMV is expected to have the following business effects
First, unlike other transportation modes requiring large investment in new infrastructure, the DMV uses existing infrastructure, cutting costs such as initial investment for purchase of vehicles and wayside equipment, running costs such as fuel, and maintenance costs for upkeep of cars and tracks. Compared to railway rolling stock, vehicle purchase expenses are anticipated to be 80% lower, vehicle maintenance expenses 25% lower, and power costs 80% lower (Figure 8). Thus, huge cost reductions can be expected.
Second is increased convenience and service. Railways are linear means of travel while roads are planar, requiring railway passengers to change modes to reach their destination. The DMV allows passengers to reach their destination in the same vehicle (Figure 9). The DMV is also practically barrier-free, helping create a new transport paradigm for aging societies.
Third is creation of new demand because the DMV can serve new areas outside existing rural networks, such as airports, urban LRTs, and tourist spots (Figure 10) to support regional revitalization.
Furthermore, in track sections, passengers reach destinations quicker than on congested roads, so the punctuality and reliability of railways can be used as business tools again (Figure 11).
Also, the flexibility of DMV routes frees it from disruptions during problems such as washed-away tracks or roads buried under snow. In other words, the DMV supplements the need for alternate modes and other weak points of railways. While railways are often seen as environment friendly, they are not in rural sections where large and heavy rolling stock is carrying only a few people each day. Since the DMV only uses about 30% of the fuel of a conventional diesel railcar (Figure 12) it is much more environment friendly on rural railways.
|Photo: Forward coupling
Photo: Reverse coupling
Figure 7: DMV Characteristics and Features
Figure 8: Effective Use of Stock (Lower Cost/ Energy)
Figure 9: Increased Convenience and Service (Seamless Railway and Road Services)
Figure 10: Creating New Demand
Figure 11: Congestion Avoidance
Figure 12: DMV Energy Conservation
Approach to Trial Passenger Operation
Trial passenger operation of the DMV has been underway
since 4 April 2007 on the Senmo Line between Mokoto
and Hamakoshimizu (Figure 13). The operation follows a
circular route with a single car, composed of rail from
Hamakoshimizu to Mokoto (about 11 km) and road from
Mokoto to Hamakoshimizu (about 25 km). Three round trips
are made each day in between conventional train services
(time sharing). One round trip takes about 1 hour. Maximum
speed on tracks is 70 km/h, and is at the posted legal speed
limits on roads.
Efforts to Achieve Full-scale Commercial Use
The current focus for expanding introduction of the DMV is
development of a new model with increased capacity and
development of an operation safety system. Automakers have
cooperated in supplying larger microbuses for 25 persons or
more. The two photographs opposite show the new DMV test
car model (DMV920) completed in June 2008, with capacity
for 28 persons demonstrated at the G8 Hokkaido Toyako
Summit. Basic operation data will be collected from the
DMV920 and another new model with capacity for more than
25 persons will be developed targeting full-scale commercial
operation in about 3 years.
The DMV was born from a shift in thinking and creativity, as well
as from a sense of urgency to keep rural railways operating.
However, many issues remain for using it an as effective
transport mode suited to the community. Most importantly,
users, operators, and government must work together to
solve problems presented by an aging society and growing
private automobile use. Significantly we must think about how
to use the DMV from the standpoint of creating a far-sighted
transport network. The current situation sees users avoiding
railways, operators in a difficult business environment, and
government in a difficult financial situation. To create a viable
transport network, local users must understand the DMV and
view it as their own railway, the community’s railway, and as
a method for restoring their community. As the operator, we
must make the maximum self-supporting efforts and raise
service levels. For its part, the government must recognize
the limits of users and the operator and help support a
new transport network for the community. As expressed by
naming it Darwin (Figure 15), there are hopes that the DMV
will engender technical, community, and policy innovations.
Present passenger trials are being used to verify future
expanded DMV introduction. On the other hand, trials do not
use all the DMV’s characteristics and features sufficiently and
as many people as possible should be allowed to take test
rides and give feedback, so development can be stepped up
in anticipation of commercial operations in 3 years with
expanded forms of operation in the future.
|Photo: Exterior of new DMV test car model
Photo: Interior of new DMV test car model
Figure 13: DMV Trial Passenger Operation Section
Figure 14: DMV Operations Safety System
Mr Hirohiko Kakinuma is Vice President of JR Hokkaido. He joined Japanese National Railways in 1969 and moved to JR Hokkaido when the company was established in 1987. Prior to his current position, he served as the Executive Managing Director, and General Manager of Railway Operation Headquarters.