Optical Flow Switching

Chan, Weichenberg, and Medard Optical Flow Switching. A proposed communications protocol, but one which has some insights for transportation (if not immediate applicability)

Motivated by the minimization of network management and switch complexity in the network core, flows are serviced as indivisible entities. That is, data cells comprising a flow traverse the network contiguously in time, along the same wavelength channel, and along the same spatial network path. This is in contrast to packet switched networks, where transactions are broken up into constituent cells, and these cells are switched and routed through the network independently. Note that in OFS networks, unlike packet switched networks, all queuing of data occurs at the end users, thereby obviating the need for buffering in the network core. Core nodes are thus equipped with bufferless optical cross-connects (OXCs). OFS is a centralized transport architecture in that coordination is required for logical topology reconfiguration. However, OFS traffic in the core will likely be efficiently aggregated and sufficiently intense to warrant a quasi-static logical topology that changes on coarse time scales. Hence, the centralized management and control required for OFS is not expected to be onerous. The network management and control carried out on finer time-scales will be distributed in nature in that only the relevant ingress and egress access networks will need to communicate.

(emphasis added)
So instead of storing and buffering (on-road queueing), they allocate the whole path between origin and destination to the flow (a trip).
Of course, since this is communications, there are some things they can do that transportation cannot:

If any errors are detected, a request for retransmission of the whole file is done via feedback to the transmitter.

(Sorry, your trip didn’t work out, please have your clone repeat the trip).

Is This the Craziest Bridge Ever Designed?

From Gizmodo Is This the Craziest Bridge Ever Designed?
How to change from driving on the left to driving on the right:

Is This the Craziest Bridge Ever Designed?I don’t know if the “Pearl River Necklace bridge is the craziest bridge ever designed, but it sure looks like the most twisted one. It’s a clever solution to a very real and obvious problem, however.

The bridge is part of a proposal by NL Architects to connect Hong Kong with mainland China. To do that, they had to solve a problem: In Hong Kong, people drive on the left side of the road. In mainland China, they drive on the right side. Here’s the solution: A road flipper that physically twists the roads over each other.

Is This the Craziest Bridge Ever Designed?

I hope the project goes forward, because I’ve always wanted to drive in a gigantic Scalextric. [Design Boom]”

Street grids

Human Transit has a nice post in praise of standard street grids.

Minneapolis Orbital Line

Continuing a series on circulatory transit routing, there is a difficulty providing services in the “suburb-to-suburb” market. The best markets will still be those with major attractions. This route connects a number of education, retail, and employment destinations, as well as connecting all of the radial transit routes emanating from Minneapolis (and some from St. Paul).

Starting on the east side, the line runs north to south from Rosedale Mall, down Snelling Avenue past HarMar, to the University of Minnesota St. Paul campus and State Fairgrounds, south to Energy Park, back to Snelling Avenue past Hamline University, intersecting the Central Corridor, down to Grand Avenue and Macalaster College, along Randolph to St. Kate’s, down Fairview through Highland Park, down Edgcombe Avenue to 7th Street (intersecting, and sharing right-of-way with a 7th Street/Fort Road line), over to Hiawatha LRT, where it shares Right of Way under the Airport. Crossing the River will remain a costly proposition given the narrowness of the existing bridge.
On the south side, it leaves the Hiawatha LRT at Mall of America, and runs along American Boulevard south of I-494 in Bloomington. (the choice of above or below I-494 is tricky, but there seems to be more activity south of the beltway, and it better serves potential park-and-ride).

The line turns North at Edinborough Way and moves over to France Avenue, where it passes Southdale Mall and Fairview Hospital, serving Edina. It runs through the 50th and France district, and then cuts across to the Excelsior and Grand area, following 36th Street until it intersects with Wooddale Avenue, intersecting the Southwest LRT. It proceeds north on railroad RoW to the Cedar Lake trail. It turns north at Park Place Boulevard, with a stop at the new West End development. The line follows Xenia Avenue north to another railroad RoW, and crosses Theordore Wirth park. It runs along Plymouth Avenue until Penn Avenue (where it intersects the Inner Circle), and turns north on Penn until Lowry Avenue.

The Orbital Line follows Lowry Avenue across the Mississippi River, turns south at RR RoW, and then east through Northeast Park and along Ridgway Parkway. It then follows frontage roads of I-35W until it reaches Rosedale Mall.

As with any hypothesized or “fantasy” transit line, all routings are first order approximations and many tens of millions of dollars in design will need to be spent to establish final alignments. There are an infinite number of possibilities (and a very large number of realistic possibilities), this seems from a cursory inspection to be some reasonable routes that have a shot at doing relatively well on an efficiency metric (benefits > costs), though I can make no guarantees of either absolute efficiency or optimality.

Saint Paul Circle Line

The Iron Law of the Twin Cities is that if Minneapolis has something, Saint Paul gets one too (and vice versa). The examples are numerous (arenas, campuses of the University of Minnesota, branches of I-35, chapters of the American Automobile Association, and so on).
In a previous post I posited a Minneapolis Circle Line . Of course Saint Paul would want to get in on the action.

I have drawn two possible fixed route, exclusive(ish) right-of-way transit lines (an Inner Circle and an Outer Circle), along with the already planned Central Corridor. I have not shown other possible lines, presumably radial, that would extend from Saint Paul (one imagines one on 7th Street/Fort Road to the southwest, a streetcar along Grand Avenue, something along Robert Street to the South, something to the west, northeast, and northwest.

The Inner Circle follows the Central Corridor line beginning at Marion Street but continues on University past the Capitol, past Regions Hospitalacross I-35E to Lafayette Road, goes south down Lafayette Road across I-94, and runs behind the proposed St. Paul Saints stadium through Lowertown, meets the Central Corridor again at Union Depot, and then jogs over to Kellogg Boulevard to run past RiverCentre, Xcel Energy Center, the Science Museum, the History Center, near the Cathedral, and up Marion Street back to University Avenue. It would serve re-developable areas near Lafayette road and Marion Street, and major attractions in the city.

The Outer Circle I have broken into two sections for convenience: North and South.
The Outer Circle (north) begins at the Dale Street station on the Central Corridor, runs north to the Pierce Butler route corridor, and goes east parallel the existing railroad tracks, behind the Minnesota Transportation Museum, across I-35E, and then south to University Avenue where it meets the Inner Circle alignment. It serves
The Outer Circle (south) also begins at the Dale Street station, runs south to Summit Avenue (I assume it would share right-of-way with the “Grand Avenue” streetcar should such a thing exist), proceed down Summit Avenue, to Ramsey Street, past United Hospital, serving the West Seventh area. It would turn south on Smith Avenue, cross the Mississippi River, to George Street, serving the West Side. It would proceed East on George Street to Cesar Chavez Street, and then Ada Street. It would cross the Lafayette Freeway and run along the edge of the St. Paul Airport. Here is the expensive part: a new river crossing would need to be constructed to get from the south to the north banks of the Mississippi River. The line would climb up Mounds Boulevard, serving Dayton’s Bluff and Metropolitan State University, and then run southeast along 7th Street/Fort Road, to the Inner Circle.

Rings make the most sense in the context of existing (or future) radials, allowing cross-traffic in cities and shortening travel times for those not going downtown. Given that St. Paul CBD has about 3% of the region’s employment (~40,000 jobs) (1990 statistics), new systems should not focus exclusively on such a small market, but should better help travelers reach diverse destinations across the city.

Minneapolis Circle Line

I have recently been thinking about the backbone transit network of the Twin Cities.

The existing and soon-to-be-built LRT lines (Hiawatha, Central Corridor, Southwest Corridor) all radiate from downtown Minneapolis. The same is true of the one Commuter Rail line.
Examining the proposed Minneapolis Streetcar System one again sees the downtown orientation (aside from the Midtown Greenway Streetcar line).
Most Minneapolitans, do not work downtown. Most do not take shop, entertain themselves, or do other things downtown very often.

Many other cities have adopted Railway loop lines , which circle around downtown at some radius. These cities include Berlin, London, Sydney, Melbourne, Brisbane, Glasgow, Madrid, Beijing, Shanghai, Tokyo, Osaka, Oslo, Seoul, Chicago, and Moscow. The advantage is that travelers do not need to go all the way into the center to go to a destination on another spoke.
Thinking about network topology in the Minneapolis case, I hypothesize a Minneapolis Circle Line service. There are several objectives in mind
(1) Maximize destinations served outside of downtown.
(2) Minimize construction costs, use existing (or to be built) alignments where possible
(3) Minimize interference from traffic, avoid on-street rights-of-way where possible.
(4) As a service, it can utilize existing tracks but go to different destinations. It separates the requirement that the line and services on the line be identical.
To that end, there are several major sections of the service:
(A) The south-side runs on the proposed Midtown Greenway Streetcar
(B) The west-side runs along the proposed SW LRT right-of-way from the intersection of the Midtown Greenway to Penn Avenue.
(C) The Penn Avenue section runs from the SW LRT Penn Station to Plymouth Avenue
(D) The north-side runs on Plymouth Avenue across the Mississippi River
(E) The northeast section runs through Boom Island park to Main Street/St. Anthony Main. If done as a “Heritage” Transit line, it could add to the qualitative attractions of this largely pedestrian zone.
(F) The southeast section follows from Main Street along the Granary Road right-of-way across the north side of the Gopher Stadium. Part of this is the Northern Alignment from the Central Corridor studies. However it would take advantage of its location and have stops at the new developments in the University Bio-technology corridor.
(G) The east section follows 25th Ave SE south to the railroad right-of-way paralleling and crossing I-94 to 27th Ave.
(H) The section passes through the five-way intersection at Franklin Avenue and East River Road to cross the Mississippi River on the Franklin Avenue Bridge.
(I) The route follows Franklin Avenue to 26th Avenue S, turns south, to meet the Midtown Greenway extended just past the Lake Street Station on the Hiawatha Line.
(*) Some alternative routings have been drawn as well.
The route thus connects Seward, Midtown, Phillips, Uptown, Lake Calhoun, Kenwood, Bassetts Creek, Harrison,Sumner-Glenwood, Near North, North Loop, East Hennepin, St. Anthony Main and Nicollet Island, Marcy-Holmes, Dinkytown,the University of Minnesota, Stadium Village, and Prospect Park, and Cedar- Riverside.


I have not tested this hypothesis in terms of potential travel demand. I do not have a perfect routing that inherently beats all others, it is a question of trade-offs and values. However the notion of non-radial services needs to be raised as the Twin Cities go forth on the biggest rail construction boom since the 19th century.

The Flattening Internet Topology: Natural Evolution, Unsightly Barnacles or Contrived Collapse?

Bill St. Arnaud finds: The Flattening Internet Topology: Natural Evolution, Unsightly Barnacles or Contrived Collapse? by Phillipa Gill, Martin Arlitt, Zongpeng Li, and Anirban Mahanti. The full article can be found here (pdf).

In this paper we collect and analyze traceroute measure- ments1 to show that large content providers (e.g., Google, Microsoft, Yahoo!) are deploying their own wide-area networks, bringing their networks closer to users, and bypassing Tier-1 ISPs on many paths. This trend, should it continue and be adopted by more content providers, could flatten the Internet topology, and may result in numerous other consequences to users, Internet Service Providers (ISPs), content providers, and network researchers.

Designing highways the slime mould way

From New Scientist: Designing highways the slime mould way


Jeff Jones and Andrew Adamatzky, specialists in unconventional computing at the University of the West of England in Bristol, wondered if biology could provide an alternative to conventional road planning methods. To find out, they created templates of the UK using a sheet of agar on which they marked out the nine most populous cities, excluding London, with oat flakes. Then, in the place of London, the pair introduced a colony of P. polycephalum, which feeds by spawning tendrils to reach nutrients, and recorded the colony’s feeding activity (see picture).
Most of the resulting “maps” mimicked the real inter-city road network, but some offered new routes. For instance, the motorway between Manchester and Glasgow passes along the west coast of the UK, but the slime mould preferred to travel east to Newcastle and then north to Glasgow ( /arxiv.org/abs/0912.3967 ). “This shows how a single-celled creature without any nervous system – and thus intelligence in the classical sense – can provide an efficient solution to a routing problem,” says Jones.

Agent-Based Model of Price Competition and Product Differentiation on Congested Networks

Recently published:
Zhang, Lei, David Levinson, and Shanjiang Zhu (2008) Agent-Based Model of Price Competition and Product Differentiation on Congested Networks. . Journal of Transport Economics and Policy Sept. 2008 42(3) pp. 435-461. [download]

Using consistent agent-based techniques, this research explores the welfare consequences of product differentiation on congested networks. The economic analysis focuses on the source, evolution, measurement, and impact of product differentiation with heterogeneous users on a mixed ownership network. Path differentiation and space differentiation are defined and measured for a base scenario and several variants. The findings favour a fixed-rate road pricing policy compared to complete pricing freedom on toll roads. It is also shown that the impact of production differentiation on welfare is not always positive and depends on the level of user heterogeneity.