Stroad

Share the Road

stroad is a pejorative portmanteau of street and road that was coined by urban planner Charles Marohn in 2011 to describe paved traffic structures in the U.S. that are a bad combination of two types of vehicular pathways.

According to Marohn, a stroad is part street—which he describes as a ‘complex environment where life in the city happens,’ with pedestrians, cars, buildings close to the sidewalk for easy accessibility, with many (property) entrances / exits to and from the street, and with spaces for temporary parking and delivery vehicles—and part road, which he describes as a ‘high-speed connection between two places’ with wide lanes, limited entrances and exits, and which are generally straight or have gentle curves.

In essence, Marohn defines a stroad as a high-speed road with many turnoffs which lacks safety features. In the commentary, Marohn states that stroads do not function well as either a street or a road. According to Marohn, the problem with stroads is that engineering codes tend to emphasize speed and traffic flow rather than safety, so that stroads try to be ‘all things to all people’ but end up failing in every way as a result.

The Las Vegas Strip is an infamously clogged stroad in Clark County, Nevada, that forms part of the Las Vegas Boulevard (part of Nevada State Route 604). It has been called the ultimate stroad and the word ‘strip’ was a commonly used term to describe ‘stroads’ before Marohn coined the latter term with a specific definition.

The design of roads as highways/motorways was originally modelled on the railroad, namely an efficient connection between two populated places (cities, towns, villages) with a car, while streets formed networks inside a place to move around that place with numerous different modes of transportation to make it financially productive; these two systems functioned well as long they were kept separated.

The general public is often not aware of the functional distinction that engineers (as well as dictionaries) make between streets and roads, that street names ending with ‘street’ or ‘road’ (for historical reasons) may be misleading and not align with the current de facto traffic situation, and that mixing up the functions of streets and roads causes numerous problems.

In some cases, roads become stroads due to a lack of access management implementation when facilities are expanded or widened, often with the aim of improving mobility. The road becomes a stroad over time from development adding private accessways onto the main road, increasing congestion and collisions, which thus requires traffic control additions such as traffic signals. This degrades the roadway quality in terms of mobility.

According to Marohn, the famous Champs-Élysées in Paris was effectively a stroad as recently as 2001. In the middle of the avenue were three automobile traffic lanes in either direction, ostensibly fulfilling the function of a road. A wide buffer of trees existed on either side of the road area, separating the roadway from slip lanes for slow-driving traffic. These slip lanes fulfilled the function of streets, providing access to parking, sidewalks, shops and restaurants. Because the street and road areas of the Champs-Élysées were physically separated, this stroad environment actually managed some success in allowing both safe high-speed traffic (up to 45 miles / 72 kilometers per hour) in the center roadway and a productive street environment on the sides. As of 2019, however, the slip lanes are fully pedestrianized, while the center roadway functions as a true road.

The Esplanade in Chico, California, is, according to Marohn, a rare example of a successful ‘stroad’ akin to the 2001 version of the Parisian Champs-Élysées in that buffers of trees physically separate the high-speed ‘road’ part in the middle from the two low-speed productive ‘streets’ on the sides (lined by houses which had high property values). He contrasted the Esplanade to Mangrove Avenue, a stroad just five blocks to the east in Chico that runs parallel to the Esplanade, but has all the typical issues of a stroad in that the street and road functions are not physically separated, and the environment is low-density and much less productive, with gas stations, strip malls and other car-oriented businesses. Unlike Marohn, however, Amsterdam based Jason Slaughter, a Youtuber that focuses on urban planning (‘Not Just Bikes’), does not categorize such traffic situations as a ‘stroad’, but as ‘a road with streets on either side to access houses.’

Stroads often do not take into account how human psychology usually determines the speed at which people drive based on the road conditions they observe. Stroads in North America typically have designated speeds between 30 and 45 miles per hour, but in practice, motorists usually drive 20 to 55 miles per hour on stroads. Simply reducing the posted speed limit (PSL) with a traffic sign, which is a widely adopted strategy attempting to prevent motorists from driving dangerously fast, may not work in practice ‘if the road conditions suggest that the PSL is too low, [because] drivers may simply ignore it.’

A better strategy to make people comply with the legal speed limit is to design roads and streets in a way that they are ‘self-explanatory’. Self-explaining roads and streets use physical and perceptual cues (also referred to as traffic calming), which lead people to automatically drive more slowly and cautiously wherever they perceive that to be necessary for their own safety, as well as that of others, especially more vulnerable road users such as pedestrians and cyclists. Such cues include ‘narrower lanes, tighter corner radii, gateway treatments, changed roadway surface materials and appearance, mini roundabouts and other speed management techniques’ such as speed bumps. The typical lack of these cues on stroads causes motorists to drive much faster than is safe to do in the environment they are in, with many entries and exits creating points of conflict and potential collisions, especially at higher speeds.

Although stroads facilitate the goal of making all destinations reachable by car, they also practically force everyone to use (and own) a car, and thus increase car dependency (at the cost of walkability and easy use of public transport), while not necessarily making travelling by car more efficient. Despite the high speeds that stroads were designed for, which has made them needlessly dangerous, in practice they frequently end up being clogged with cars seeking access from the many entrances, so that the average speeds on stroads are low due to traffic congestion. Widening stroads to counter congestion usually only leads to induced demand and extra costs.

Marohn (2017) stated that stroads ‘are enormously expensive to build and, ultimately, financially unproductive.’ This is because ‘stroads are built to a highway standard, their lanes are very wide, and there are never [fewer] than four lanes’ and they usually take up extra space for shoulders and clear zones. Stroads feature many more entrances and exits than limited-access highways and roads and thus require more turning lanes, and because stroad vehicle speeds may be higher than on a street, the turning lanes are much longer to allow vehicles to decelerate and reduce the risk of rear-end collisions; this means stroads require more and longer turning lanes, which are more expensive to build and maintain and take up more space than streets and roads do. The high frequency of accesses to a stroad with much traffic often prompts the construction of traffic lights at intersections, which may cost up to 250,000 US dollar to build (excluding maintenance costs).  An extreme example of this is found on the intersection of Charleston Boulevard with Decatur Boulevard in Las Vegas, which features seven approach lanes, each of which has traffic lights.

The larger size of stroads compared to streets and roads means they require more space which needs to be purchased, flattened and asphalted, which reduces the property value of the land, increases the cost of flood protection infrastructure, and asphalt and traffic control system maintenance costs.  Compared to households along urban streets, stroads tend to double the costs that households pay on the construction and maintenance of infrastructure, as well as the delivery of public services, while the tax revenues per acre of properties along stroads pale in comparison to urban commercial streets. The space taken up by stroads, as well as the large areas dedicated to parking lots at the destinations of cars using stroads, result in low-density land use (typical for urban sprawl). This makes stroad environments financially significantly less productive and tax-generating than a street, but with significantly more infrastructure and thus high-cost per area maintenance costs, so that they become a net-negative and financial burden for cities, because they cannot sustain themselves.

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