This blog is about highways in cities, more specifically state highways and arterials passing into and through urban areas.  While there is certainly an interest by the state in maintaining connectivity throughout the state, there should also be a recognition that highways are fundamentally incompatible with cities.  All too often the metrics used by practitioners favor highways over cities.  We explore these corrections to make highways in cities more “complete”.

—Michael King and Rick Chellman

Highways should not go through cities

Cities have always served as gathering places for people.  Connections between cities have always been important.  When those connections are and were made on foot, powered by animals, by cycle, by rail, or by water, they are and were more compatible with the internal working of cities.

When highways are designed for motor-driven vehicles, the design speeds are orders of magnitude faster than anything compatible with people on foot.  Highway speeds, indeed speeds in excess of 35 mph (56 kph), are unsafe for pedestrians.  The space needed for the curves, banking and transitions required to manage highway speeds consume vast areas of land that is otherwise better used in urban settings.  They divide cities just as surely as a wide and fast river.

Highways can connect between cities, but should not go into or through cities.  

Travel time

Travel time measures the time it takes to drive from point A to point B.  It is commonly used to rank cities by measuring commuting time, which is one type of travel time, in that case the time to travel from home to work.  

While there is nothing inherently wrong measuring the required time to travel between locations only - in vehicles, this metric diverts attention from several larger policy matters. As noted, highways should not pass through cities because when they do, in pursuit of lower commute times, the negative impacts of this higher-speed travel on the surrounding areas is ignored or downplayed as of lesser importance.  

The quality of travel time and the impacts of any mode of travel on the areas it passes through must be considered in route and mode choice policy decisions.  A slower speed of travel that is safe, comfortable and a welcomed part of a particular neighborhood will likely require more travel time in an absolute sense to pass through, but that time will be much more greatly enjoyed by both the travelers and the residents being traveled by. Conversely, when the context of travel is so unpleasant that its duration must be minimized, the only metric that matters is travel time: again, this is much too simplistic and an outmoded way of thinking.

A related topic to this focus on travel time is the disconnect between working places and living places - see land use and urban design discussion below.

Motor Vehicle Level of Service

Since its inception, motor vehicle level of service has measured delay to drivers, especially at traffic signals.  More recently, multi-modal LOS has attempted to evaluate intersections across modes, but it is still something of a work in process due to quantitative complexities. Multi-modal quality of service, even if primarily subjective, should be a part of the complete street planning process.  Multiple turning lanes, for example, in an area with or anticipated to have reasonable pedestrian activity is likely a poor idea.

Here are a few ideas to make LOS analyses more holistic:

• only evaluate LOS on a network level - minimum of 10 intersections

• cap number of lanes, including turning lane at intersections - maximum three per direction

• cap signal cycle length - maximum 100 seconds

• retime signals as per modal hierarchy - pedestrian, transit, bicycle, vehicle

Traffic signals at night

Traffic fatalities are typically over-represented at night.  Speed is the significant determinant in the severity of any injuries and along with impairment, a high determinant of whether a crash occurs.  Traffic signals along arterials are often activated, meaning they stay green for the main line unless there is cross-traffic.  At night there may be little cross-traffic, so drivers on the arterial see a “green wave” of signals that do not change.  This leads to higher-often very dangerously higher-vehicle speeds during the off peak hours.

To counter this, traffic signals should be fixed time at all time, or have off-peak timing designed to slow through traffic to reasonable speeds.  Another possibility to consider is to have all-flashing red signals at night, in effect creating all-stop conditions.  While stop signs are not meant to manage speeds, this may be safer than an all-green. 

Access Management

According to the @USDOTFHWA, access management is the “proactive management of vehicular access points to land parcels adjacent to all manner of roadways.” Many state DOTs describe access management principles in terms of miles.  For example, @MODOT states that traffic signals on principal arterials in urban areas should be spaced at least a ½ mile (2640’) apart.  Median openings can be ¼ mile (1320’) apart.  Driveways are allowed every 1/12  mile (440’).

With all due respect to access management principles, there are other reasons to interrupt the flow of traffic.  For example, blocks in older American cities are typically on 1/20 mile (264’) or 1/16 mile (330’) increments.  As such there is potentially a need for people to cross the street at each of these streets.  Local bus stops can be spaced every ¼ mile (1320’), ensuring a five minute walk to the stop.  It is very hard to argue against crosswalks at bus stops.  Best practices places bicycle facilities at 1/8 mile (660’) intervals.  

Streets evolve and there is constant tension to adjust the operations on “highways” in cities that, in context, should be treated as what they are: city streets.  State routes that were once 2-lane blacktops surrounded by farms, are now multi-lane boulevards surrounded by city.   Legacy driveways confound practitioners.  Intermittent on-street parking needs to be organized.  The notion that drivers can proceed unimpeded for miles on end becomes increasingly untenable.  There is a limit to managing access.

Bypasses and Functional Classification

Many towns in the US have a bypass, ring road or parallel highway, bypassing the historic route through town.  However, after the bypass is built, the bypassed road is not downgraded or re-designated, often remaining a “Principal Arterial”.  Often this is because of funding, as many federal and some state funds are ties to miles of streets and highways by type of functional classification. 

The creates many problems in mixed-use places desiring to enhance pedestrian and other non-motorist travel.  The ”Principal Arterial” most want to call Main Street still must adhere to state and federal highway standards and guidelines, which are meant to facilitate traffic through town, not to town.  In addition, these standards and guidelines lead to undesirable higher vehicle speeds (see above).

A rather successful town-county cooperation is South Orange Avenue in @southorangenj.  As documented in Flexible Design of New Jersey’s Main Streets,

“…the town passed a resolution pledging to return the street to its previous condition if the [road diet] failed in some respect. The resolution, however, never defined objective criteria of success or failure.”

25 years on, the road diet remains.

Other positive examples exist. Hemphill Street in @CityofFortWorth is a parallel route being returned to its previous condition.  In the 1970’s it was a tree-lined two-lane arterial.  A few blocks away sits I-35W, which was to be expanded.  In anticipating the overflow traffic during construction, Hemphill was widened.  The trees were removed and replaced with a 2nd travel lane.  And yet, once I-35W was expanded, the wider Hemphill remained.  It remained a hot, desolate strip of concrete.  Only years later was the 2nd lane removed, replaced with bike lanes.  There are still no trees, but it is a start.

Land use and urban design

The practice of transportation planning focuses largely on providing mobility for people and goods – often without proper regard for where and why the people and goods are traveling.  It is a somewhat linear and non-urban process.  A neighborhood or office district is created and roads are added, not unlike plumbing (hence #trafficplumbers).  The result is increased traffic demand because the destinations are dispersed.

Land use planning and urban design can set the table for mobility success, often by organizing land use and urban design in walkable proximity.  This reduces the need for multiple arterials, especially in cities.  The first consideration is density.  With sufficient density, goods and services are within walking or cycling distance.  Second is organization.  If the built up area is organized along a transit corridor, then taking transit becomes commonplace.  Third is layout.  If streets and paths are properly arranged and detailed to facilitate walking/cycling/transit, then people will drive less.  Envision an ideal college campus centered around a quad with more paths than streets.  

City building is a shared exercise.