The principle of universal access – which provides cyclists and pedestrians reasonably safe and efficient access to all destinations – is entirely compatible with existing traffic science and good traffic engineering practices designed to facilitate both mobility and access. This essay describes how this compatibility is accomplished and how conflicts and confusion can be avoided.

Streets and highways that serve different uses are usually designed differently. Traffic engineers may optimize one roadway to carry vehicles long distances at high speeds with minimal junction conflicts, while another road may be designed for slower speeds with many driveways and intersections. The tradeoff of convenience for through-traffic versus connectivity for local destinations is often referred to in traffic engineering literature as a tradeoff in mobility versus access. A controlled-access freeway offers maximum mobility and no local access. A cul-de-sac offers maximum access and minimum mobility. Most roads are a compromise somewhere in between.

The Highway Capacity Manual (HCM) defines an "access point" as follows:

Access points generate turning, entering, exiting, and crossing traffic movements, which tend to slow traffic on the roadway. When access points such as intersections are signalized, significant reductions in the average travel speed of through traffic may occur. Minimizing the number of access points per mile of the roadway tends to increase the average travel speed of through traffic in order to improve mobility. Higher-speed arterial roads are called "limited-access" roadways when they facilitate mobility through a reduced number of access points.

Note that with the exception of some interstates and other controlled-access freeways, limited-access thoroughfares are completely legal for use by pedestrians and bicyclists. Limited-access status alone does not imply prohibition of any user group. In suburban areas, limited-access arterial roads are often the only routes to important destinations such as shopping centers, schools, high-density residential developments, and major employers. Arterial roads usually service popular destinations, and high-volume roads are magnets for major commercial developments such as shopping centers, which generate even more traffic. Ironically, the fewer access points there are on an important arterial road, the more important those access points are to everyone in the community including utilitarian pedestrians and cyclists.

Also note that some of the features of well-designed limited-access roadways can offer superior safety and convenience benefits to pedestrians and cyclists. Reducing the number of cross-traffic locations reduces right-angle collision hazards (the most common crash conditions) for both motorized and non-motorized users. Multiple travel lanes in each direction allow motorists to pass bicyclists without conflicts with opposite-direction traffic. Same-direction traffic is less of a risk for lane encroachment, and if the outside through lane is wide enough, drivers of motor vehicles need not move into the adjacent lane at all. A reduced number of intersections also allows cyclists to enjoy the benefit of faster average travel speeds for cross-town trips. Raised center medians of adequate width provide pedestrians with a refuge location when crossing roads at unsignalized locations. Such refuge islands allow pedestrians to cross the street in two stages, with each stage being only half as wide and with traffic coming from only one direction. This means adequate gaps in traffic are easier to find and street crossings are more convenient. Consequently, the crash rate for pedestrians crossing roads with raised medians is half as high as on similar roads without raised medians.

One disadvantage of limited access roads is that long distances between access points and high volumes of fast motor traffic tend to make walking and cycling on such roads unattractive to some people, especially to those who have the alternative of automobile use. If the design of the roadway does not consider non-motorized traffic, use of the road by pedestrians and cyclists is often limited to those who do not have cars or who are highly dedicated to non-motorized travel modes. Another disadvantage is that the speed of motor traffic creates much more severe injuries to pedestrians and cyclists in the event of a collision. This means that collision prevention for pedestrians and cyclists via good engineering, education and law enforcement is extremely important.

Unfortunately, the low number of pedestrians and cyclists found on limited access roads has sometimes been used as an excuse by roadway engineers to ignore the safety and comfort of pedestrians and cyclists in the design of those roads. Sidewalks are sometimes omitted, or traffic signals are not timed long enough to allow pedestrians to safely cross intersections. Demand-actuated traffic signals on side streets and in left-turn lanes may not respond to bicycles. In a few cases, omission of safety features for pedestrians and cyclists has been done deliberately to discourage walking and cycling on limited access roads. As a result, transportation planners, law enforcement officers, and road users sometimes confuse lack of design consideration with prohibition of walking and bicycling. These actions are all violations of universal access and infringe upon the travel rights of citizens without cars. The importance of the destinations located on such roads and the severity of injury in the event of a collision demands that appropriate design considerations be made to protect the safety of those without cars even though their numbers are not large. It is the speed and volume of motor traffic that demands design consideration for legal pedestrian and bicyclist traffic; when divided by the number of vehicle miles traveled the cost of construction of better facilities is not unreasonable.

Universal access dictates that if an access point is provided for motor vehicle traffic, reasonably safe accommodation must also be provided for pedestrians and cyclists. Anything less constitutes unacceptable discrimination against non-motorists. The number of local access points may be decreased to increase mobility, but only when the number drops to zero, in the case of controlled access freeways where walking and cycling are prohibited, can walking and cycling modes be safely ignored.

Designing roads and intersections for minimum or improved accommodation of pedestrians and cyclists can have significant short-term costs. Construction costs for sidewalks, pedestrian signals, bicycle-sensitive signal sensors, medians, wide outside lanes and/or paved shoulders are higher than for roads lacking these features. Long pedestrian clearance intervals on very wide streets can reduce green time for through traffic and consequently reduce vehicle capacity. When these costs are considered in the planning stages of roadways and development, however, it is often possible to minimize the costs and maximize the benefit of the improvements through better street design and land use planning. For instance, building multiple redundant routes with fewer lanes per street disperses traffic, increases efficiency, eliminates single points of failure on the event of traffic accidents, and reduces the effect of pedestrian clearance times on traffic throughput. Reducing the number of access points can offset the increased cost per access point. Arterial access points may be completely eliminated in favor of sealing a corridor as a controlled access freeway and providing access via a redundant system of local roads that are friendly to pedestrians and cyclists. Grade-separated crossings at arterial roads preserve the benefits of a redundant, connected street system while enhancing arterial mobility.

Future land uses will adapt to the provisions of access to the transportation system. When these access points are reasonably safe and accessible for pedestrians and cyclists, the maximum benefits of walking, cycling and transit modes can be realized. But when access points are provided on busy arterial roads where walking and cycling modes are not design considerations, land uses will gravitate toward patterns that not only increase automobile dependency, but also generate traffic patterns that adversely affect mobility on the arterial roads as important destinations and large volumes of motorists are attracted to them.