Colorado motorists have spent a long time waiting—much of it behind the wheel—for congestion to ease along a stretch of I-70 extending from Denver into mountain resort towns.

等待时间通常在夏季和冬季周末最糟糕的情况下，很快就会结束。科罗拉多州的运输部（CDOT）沿着岩石12英里的走廊建造了一条峰值的，峰值的内肩车道（PPSL），该走廊从爱达荷州斯普林斯的退伍军人纪念隧道向西延伸至帝国交界处。

科罗拉多州Greenwood Village RS＆H的Colorado-North建筑，工程和检查负责人Ray Strandberg表示，这座耗资7000万美元的车道的建设始于2019年7月，将于2月完成。

在某些方面,该项目代表了第二轮for CDOT; HDR Engineering Inc., the engineer of record; and RS&H. Those firms participated in the completion of an eastbound PPSL along the same I-70 corridor in 2015. The eastbound lanes proved particularly nettlesome, in part because many motorists depart the mountain resorts simultaneously on Sunday afternoons to make the trip back to Denver.

Conditions have improved considerably with the new eastbound inner lane, which captures up to 8.2% of peak-period traffic throughout the winter (about 152,000 vehicles) and 10.5% of summer traffic, roughly 105,000 vehicles during that period, resulting in average corridor speeds of 45 mph, according to the High Performance Transportation Enterprise (HPTE), an independent government-owned business unit within CDOT.

一个下坡的口号

CDOT的项目工程师杰夫·汉普顿（Jeff Hampton）表示，西部周末的交通最初更加分散，尽管交通拥堵的人口迅速增长，但这种交通拥堵的峰值峰值流量将台阶置于停滞状态。汉普顿说：“几乎所有交通流量都流过走廊，要么从科罗拉多州的中央山脉到达或返回。”“丹佛都会区和山脉之间没有很多替代路线。”

像其前身一样，西行PPSL仅在高峰期（在这种情况下）在周五，周六和周日选择小时，而与周六和周日的部分地区相比，向东行驶的交通。总而言之，对西行PPSL的使用将限制为每年125天，就像对东行PPSL的使用限制为每年100天一样。在其他日子里，PPSL将像东行相机一样恢复到标准的肩车道。

Another formidable constraint called for squeezing as much space as possible from existing infrastructure to accommodate the 11-ft-wide PPSL.

“The goal was to minimize widening I-70 by maximizing the existing footprint,” says Neil Ogden, resident engineer with CDOT. The original footprint consisted of a pair of 12-ft-wide lanes, a 4-ft-wide inner way and an outer shoulder of varying widths, up to 10 ft, potentially bringing the total width to 38 ft. To construct the 11-ft-wide PPSL, CDOT required an overall width of 42 ft, including a 4-ft-wide outer shoulder and 2 ft of inner shy distance between the PPSL and the inner barrier.

Space and usage constraints were imposed because both eastbound and westbound PPSLs are classified as interim solutions for congestion. They are intended to cease operations by 2035, when alternative solutions to congestion in the corridor may be ready for implementation. As such, activities included programs and reviews to minimize the impact of the PPSLs on the environment, including a CDOT-mandated context sensitive solutions process (CSSP), performed in accordance with federal guidelines. It also included input from multi-disciplined, multi-interest stakeholders.

Provisions also called for measures to mitigate noise, light and air pollution during construction. Air-quality measures, for instance, required that vehicles and equipment employ the cleanest possible fuels and that project team members devise a fugitive dust-control program, according to Vanessa Henderson, I-70 Mountain Corridor environmental manager with CDOT.

Tight Fit

HDR的高级运输项目经理Chau Nguyen说，为了容纳PPSL，计划者在录像片段存在的区域和距离内部2英尺的区域最多分配了6英尺。额外的空间来自于没有覆盖岩层的位置，位于外肩上的新路面。另外，计划从西行和东行车道之间的草中间提取了一些空间。

Nevertheless, about 65% of the space for new pavement comes from the median area and about 35% from outside the shoulder, estimates Ned Meyers, senior project manager with Graham Contracting, Westminster, Colo., the project’s general contractor.

As work proceeds, the CSSP mandates that existing lanes remain open during the day, with partial closures limited to overnight hours. As paving vacillates from one side of 1-70 to the other, existing lane locations temporarily shift, requiring that crews realign the lanes with concrete barriers during night shifts to accommodate work zones, Meyers says. “This is definitely a round-the-clock project,” he says.

Methods and materials to construct new pavement have varied, depending on location. Installation of new pavement adjoining the outside shoulder required excavating down to subgrade—about 15 in. to 16 in. deep—followed by adding 6 in. of backfill, or base course, to the excavated space. The infill consists of a semipermeable aggregate of gravel and finer granules that promote moisture migration to subgrades, says Hampton. To achieve the final elevation of roadway, crews next paved three lifts of hot-mix asphalt totaling 9.5 in., Strandberg notes.

正在进行的工作中已经证明更多的complex. In some locations, the grassy strip sloped downward between the westbound and eastbound lanes, creating grade variations of up to 8 ft between the two. As a result, construction of retaining walls and supporting mechanically stabilized earth—or backfill—was required to create a platform for additional pavement within the median, according to Hampton. All told, the walls consist of 10-ft-wide, 6-in.-thick precast concrete panels that vary in height from 3 ft to 8 ft, depending on grade differentials.

Strandberg说，船员首先挖掘了几英寸，以构建面板的地位升级垫，然后通过提供给挖掘机的电缆将面板悬挂在适当的位置。Strandberg补充说，临时支撑支持了面板，而工人则建造了由“ 89”石头组成的毗邻的工人，该石材被压实但也足够多孔以进行排水。机组人员使用滑动牛排来放置石头和光滑的鼓辊以优化压实。

A series of metal straps at various intervals on the back of each precast panel are anchored into the backfill to join the two. Crews then topped the assembly with a 12-in.-thick reinforced concrete anchor slab to support a Type 7 concrete barrier that extends the length of the entire wall. Three inches of asphalt then will be placed upon the anchor slab to serve as pavement. Additional pavement comes from asphalt applications to a gap sited between the slab and existing roadway.

汉普顿说，总共需要大约四英里的挡土墙。

Seasonal Work

沥青应用需要大于50°F的温度，因此初始安装与2019年的夏季相吻合。由于走廊西部最西部部分的车道之间缺乏分级差异，因此从西部到东部进行了工作。斯特兰德伯格说，由于不需要固定墙，因此工作人员使用与外部肩膀相同的方法安装了人行道。在冬季开始，在挡土墙和回填方面的工作开始。

Starting this summer and extending into the fall, crews have been placing a 3-in.-thick top lift of asphalt across the existing lanes and new pavement in addition to the concrete anchor slabs. Existing lanes are being milled during nighttime hours. The underlying surface is suitable for vehicles until the final asphalt is placed.

Also included in the scope of work is scaling of select rock formations adjacent to the outer shoulder. In addition to removing loose stone, crews installed metal mesh on the sides of formations to prevent rockfalls. One area of scaling near Idaho Springs encompassed 700 ft and at heights up to 100 ft, Hampton says. Crews used expanding airbags to dislodge larger rocks. CDOT held traffic for selected times during scaling and rock operations, Hampton says.

Once scaling was complete, crews used manlifts and cranes to secure the mesh to the rock face. The operation included installing a second outer layer of draped or hanging mesh anchored above the fixed layer of mesh. “The draped mesh allows for any rock further up, say from land atop the formation, to enter a catchment area and drop between the layers to the bottom of the slope,” Hampton says.

Remaining work involves installation of tolling equipment, including microwave radar vehicle detectors and cameras that capture license plates, Hampton says. Additional lane equipment will consist of electronic signage indicating the PPSL’s status—open or closed—and variable message signs with information about traffic along the corridor.

Should all go as planned, traffic speeds on the westbound lane are expected to correspond with those of the eastbound lane, according to Kelly Brown, tolling operations manager with HPTE. Tolling helps to regulate the volume of traffic in each PPSL. In past instances, the addition of toll free lanes simply led to increased congestion without improving travel time reliability, Hampton adds.

因此，HPTE最初实施了一个基于需求的收费结构，范围从ppsl的$ 3到30美元，随着流量的增加，利率上升。但是，驾驶员一旦利率超过8美元，驾驶员避免了PPSL。结果，赫普特（Hpte）从一天中的时间内实施了6至7美元的固定损失。布朗说，西行PPSL的费用结构尚未完成。