Dallas l DART Light Rail Expansion Updates

[mfastx]

Originally Posted by lrt's friend

Of course, required capacity must be a consideration but the passenger capacity presently existing in Atlanta and Dallas can easily be handled by current LRT technology. You just have to look at Calgary's C-Train to show you what is possible with LRT. And the capacity of their system will significantly increase as they move to 4 car trains. And this is with the less than ideal surface route through downtown. The largest cities may need longer trains but I don't think you can say that heavy rail will attract more ridership on its own. The speed of service and the location of the route are more important factors. LRT generally is capable of offering the same speed of service as heavy rail if both are given an exclusive right of way. Of course, LRT is not suitable for longer distance commuter rail.

I'm not quite sure it's that simple. LRT can only be as effective as HRT if it is completely grade separated and if it's fast. Average speeds for light rail are about half that of heavy rail.

If you're going to go ahead and 100% grade separate a light rail line, and making long trains and platforms, you might as well go ahead and do heavy rail, it'll cost the same.

Atlanta's heavy rail system has over double the ridership of Dallas' light rail system, despite only being 56% of DART's track miles. The systems are very similar, both have lines stretching out the the suburbs like commuter rail.

[Wizened Variations]

Originally Posted by mfastx

I'm not quite sure it's that simple. LRT can only be as effective as HRT if it is completely grade separated and if it's fast. Average speeds for light rail are about half that of heavy rail.

If you're going to go ahead and 100% grade separate a light rail line, and making long trains and platforms, you might as well go ahead and do heavy rail, it'll cost the same.

Atlanta's heavy rail system has over double the ridership of Dallas' light rail system, despite only being 56% of DART's track miles. The systems are very similar, both have lines stretching out the the suburbs like commuter rail.

There are a couple more variables that we just don't talk much about in the US that are key to moving people on steel rail.

A) 4 track, or less preferably, 3 track stations on 2 track main lines. The ability for one train to pass another going in the same direction radically improves net ridership per hour.

This can occur any where on dedicated right-of-way. In systems with mixed street and dedicated right-of-way running, expresses can be used with the caveat that train schedules are posted in real time at each station, so that users are aware that train X has passed train Y.

In addition, 4 track stations provide the capability for trains to split into two trains, as is routinely done in France, Japan, and, Germany. More importantly, trains A and B can merge on tracks 1 or 4 while traffic runs through on tracks 2 and 3.

B) Radii of curvature. The fastest way to slow down rail traffic is to put in tight curves, particularly on dedicated right-of-way. In addition, tight radii curves both increase wheel flange wear as well as track wear significantly.

C) Higher speed switches. Trains should not have to slow down just to switch tracks- switches need to be safe at full track speed.

None of these factors necessarily mean LRT or commuter rail. Rather, such factors point out the need to consider good design above all.

[VivaLFuego]

Originally Posted by mfastx

Atlanta's heavy rail system has over double the ridership of Dallas' light rail system, despite only being 56% of DART's track miles. The systems are very similar, both have lines stretching out the the suburbs like commuter rail.

I don't have hard stats handy, but I'm pretty sure that Atlanta has significantly less road capacity (especially highways into its CBD and generally on its arterials) and higher total jobs and employment density in the general downtown+midtown area than does Dallas. Lack of road capacity --- i.e. crippling congestion --- will drive transit ridership much more strongly than the specific type of transit technology chosen.

[atlantaguy]

Originally Posted by VivaLFuego

I don't have hard stats handy, but I'm pretty sure that Atlanta has significantly less road capacity (especially highways into its CBD and generally on its arterials) and higher total jobs and employment density in the general downtown+midtown area than does Dallas. Lack of road capacity --- i.e. crippling congestion --- will drive transit ridership much more strongly than the specific type of transit technology chosen.

Sorry VivaLFuego, but not really true. Downtown/Midtown are serviced by the 14 lane Downtown Connector (the combined I-75/I-85), the 8 lane I-20, numerous very wide one-way corridors and several major arterials.

MARTA has the ridership it does because it links 4 of our 5 major business districts/employment centers with the worlds busiest airport. It's really pretty simple.

[Jasonhouse]

^I agree with you.

I think the other key is its speed. If transit can get someone there quickly and dependably, why risk getting screwed in traffic?

[Wizened Variations]

Originally Posted by Jasonhouse

^I agree with you.

I think the other key is its speed. If transit can get someone there quickly and dependably, why risk getting screwed in traffic?

You are talking about the comparative time necessary to get from suburb A to downtown B. This is a function of dedicated right of way, pass tracks for same direction trains, large radii turns (possibly banked), high speed switches, 4 track stations (in large part),high average speeds, and, desirable destination points serviced by the light rail/heavy rail, or heavy rail system.

[electricron]

Originally Posted by Wizened Variations

You are talking about the comparative time necessary to get from suburb A to downtown B. This is a function of dedicated right of way, pass tracks for same direction trains, large radii turns (possibly banked), high speed switches, 4 track stations (in large part),high average speeds, and, desirable destination points serviced by the light rail/heavy rail, or heavy rail system.

All excellent points, although I believed you missed one, i.e. station spacing. A train can achieve a higher average speed if it doesn't stop as often.

Comparing average speeds between MARTA to DART.

MARTA Red Line North, Five Points to North Springs, 11 stations, 29 minutes, 17.65 miles. Averaging 36.5 mph.

DART Red Line North, Union Station to Parker Road, 17 stations, 45 minutes, 21.15 miles. Averaging 28.2 mph.

DART Red Line North, Pearl to Parker Road, 13 stations, 36 minutes, 19.64 miles. Averaging 32.7 mph.

The difference between the DART examples is that one is eliminating one and a half miles of the street mall in downtown Dallas. DART's street mall is 1.5 miles in length, 4 stations, and 9 minutes, the trains averaging a fairly low 10 mph through it. There's a huge difference in the average speed of DART's light rail trains if we include the street mall. Where most of the slowdown occurs is when running at grade level in city streets. But light rail trains within a dedicated corridor can average close to the same speeds as metro trains, the average speeds differential depends mostly on station spacing.

[Wizened Variations]

Originally Posted by electricron

All excellent points, although I believed you missed one, i.e. station spacing. A train can achieve a higher average speed if it doesn't stop as often.

Comparing average speeds between MARTA to DART.

MARTA Red Line North, Five Points to North Springs, 11 stations, 29 minutes, 17.65 miles. Averaging 36.5 mph.

DART Red Line North, Union Station to Parker Road, 17 stations, 45 minutes, 21.15 miles. Averaging 28.2 mph.

DART Red Line North, Pearl to Parker Road, 13 stations, 36 minutes, 19.64 miles. Averaging 32.7 mph.

The difference between the DART examples is that one is eliminating one and a half miles of the street mall in downtown Dallas. DART's street mall is 1.5 miles in length, 4 stations, and 9 minutes, the trains averaging a fairly low 10 mph through it. There's a huge difference in the average speed of DART's light rail trains if we include the street mall. Where most of the slowdown occurs is when running at grade level in city streets. But light rail trains within a dedicated corridor can average close to the same speeds as metro trains, the average speeds differential depends mostly on station spacing.

I agree. That however is where express trains shine. If on the Red Line, for example, trains going in the same direction could pass one another, then, a "Minibullet Express" might average the 19.64 miles at 45 or more mph, for an average of 26.2 minutes. An express train with an average speed of 60 mph (which would be very fast for a commuter train) would take 19.64 minutes. Lower priority express trains, can be set up to hit every other, or every third station, giving the express option to all stations on a line, assuming that 1/2 of the stations have the same direction train passing option (there is a bit of scheduling math here, but the 1/2 rule is a good yardstick)

Express trains work best as the length of the line increases by lengthening the transit comfort zone, which, IMO, is around 30 minutes travel time. The more distance that can be covered in 30 minutes, the greater the potential draw.

Express trains also provide the feeling of speed.

Express trains lengthen the distance between stops on rail lines with distances a shorter distance apart.

*****************

A truly great commuter system would have high speeds on dedicated right-of-way and a hierarchy of express trains supplementing local trains. An express train with 120 mph peak speeds on well designed right-of-way and stations with the same direction train passing option, conceivably could average 90 mph. At this point, the train would cover 45 miles in 30 minutes which is far faster than can be done by auto. An East West express train link between Dallas and Fort Worth, would cover the 36 mile distance (by car) in 24 minutes, and, cover the 80 mile east/west Metroplex in about 53 minutes.

Light rail then could hook into the express line at transfer points.

Someday some metro area will do this, most likely overseas.

[Rail Claimore]

Originally Posted by atlantaguy

Sorry VivaLFuego, but not really true. Downtown/Midtown are serviced by the 14 lane Downtown Connector (the combined I-75/I-85), the 8 lane I-20, numerous very wide one-way corridors and several major arterials.

MARTA has the ridership it does because it links 4 of our 5 major business districts/employment centers with the worlds busiest airport. It's really pretty simple.

It helps when Downtown/Midtown is one of the next 5 or so largest traditional CBDs after the ones found in the 6 transit legacy cities. Others in this category are Seattle, LA, Houston, and Denver.