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All state highway systems and most of the local highway and street systems encompass several types or classes of highways. At one extreme are high-speed， high-volume facilities carrying through traffic， with no attempt made to serve abutting property or purely local traffic. At the other are local rural roads or streets that carry low volumes， sometimes at low speeds， and with a primary function of land service.
AASHTO ① Special Committee on Nomenclature gives definitions for various types of highways.Some of these are as follows：
Expressway Divided arterial highway for through traffic with full or partial control of access and generally with grade separations at major intersections.
Freeway Expressway with full control of access.
Parkway Arterial highway for noncommercial traffic， with full or partial control of access， and usually located within a park or a ribbon of parklike developments.
Control of access Condition where the right of owners or occupants of abutting land or other persons to access， light， or view in connection with a highway is fully or partially controlled by public authority.
Full control of access means that the authority to control access is exercised to give preference to through traffic by providing access connections with selected public roads only and by prohibiting crossing at grade of direct private driveway connections.
Partial control of access means that the authority to control access is exercised to give preference to through traffic to a degree that， in addition to access connections with selected public roads， there may be some crossings at grade and some private driveway connections.
The other highway types lack the feature of access control. They include：
Major street or major highway Arterial highway with intersections at grade and direct access to abutting property， and on which geometric design and traffic-control measures are used to expedite the safe movement of through traffic.
Through street or through highway Every highway or portion thereof on which vehicular traffic is given preferential right of way， and at the entrances to which vehicular traffic from intersecting highways is required by law to yield right of way to vehicles on such through highway in obedience to either a stop sign or a yield sign， when such signs are erected.
Local road Street or road primarily for access to residence， business， or other abutting property.
It should be pointed out here， however， that the freeway， as typified by the Interstate System，represents the highest type of highway facility， whose advantages include the following：
Capacity On freeways the absence of intersections or crossings at grade and the elimination of marginal friction through access control permit unrestricted， full-time use by moving vehicles， rather than restricted， part-time flow.
Reduced travel time On freeways， time losses from stopping and waiting at intersections are eliminated. In addition， most of the conflicts that contribute to accidents are eliminated， except under unusual circumstances. Drivers normally can and will travel at higher and sustained speeds.
Safer operation On freeways， elimination of conflicts at intersections and along both margins of the roadway and the barring of pedestrians from the right of way usually bring substantial reductions in accidents.
Permanence Access control along freeways prevents the growth of businesses or other activities along the roadway margin. Without access control， these activities generate unordered traffic and parking. In a short time， capacity is reduced and accident potential is substantially increased.
Reduced operation cost ， fuel consumption ， air pollution ， and noise Smoother operations and fewer stops reduce fuel consumption and other operating costs. Reduced fuel consumption in turn reduces air pollution. Smoother operation with fewer stops also greatly reduces noise， particularly that from trucks.
encompass v. 包括，围绕
abut v. 邻接，毗连，紧邻
nomenclature n. 术语
expressway n. 快速道路（部分立交）
through traffic 过境交通
grade separation 立体交叉
arterial a. 干线的，主干的，动脉的
intersection n. 交叉（口）
parkway n. 风景区干道
ribbon n. （由市区到郊区）沿干道发展的一系列建筑
preference n. 优先，选择
expedite v. 促进，派遣
obedience n. 服从，顺从
sustained a. 持续的，持久的
pedestrian n. 行人，步行者
permanence n. 永久（性）
state highway 国道
local highway 地方道路
at grade 平面（的）
right of way 通行权，道路用地
yield sign 让路标志
typify v. 作为……的典型，代表
interstate system 州际（道路）系统
marginal friction 路侧摩阻
①AASHTO （American Association of State Highway and Transportation Officials）美国各州公路与运输工作者协会