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The bridge remains closed from 5 - 8 a. It does open for vessels in an emergency. The 4. Continue on Route 17 to the I interchange in Suffolk. The bridge is free. The James River Bridge opens upon vessel demand, according to federal regulations. It does not have any periods where openings are restricted. The bridge was rebuilt in to handle increased traffic. The bridge merges I traffic traveling from Chesapeake with I traffic in Norfolk. The I Berkley Bridge will open for maritime vessel signal at 9 a.

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The bridge will not open during these scheduled times when vessels have not signaled and are not waiting for passage. The duration of the traffic stops due to the bridge lifts are dependent on maritime traffic volumes. The bridge will remain in the close position during commute periods, from 5 - 9 a.

The bridge can open upon request during the restricted hours for a vessel with a draft of at least 18 feet if at least six hours of notification has been given. Built in , the High Rise Bridge is a concrete and steel drawbridge located on I in Chesapeake. The four-lane, twin bascule span bridge carries more than two million motorists a month. The facility is the only highway-grade toll-free crossing of the Southern Branch of the Elizabeth River and can be used as an alternative to the tolled Downtown and Midtown Tunnel.

The bridge opens upon vessel demand, according to federal regulations. It remains closed from 6 - 9 a. If other composition viz. The required overlay in terms of BM could be deduced from the curve for the characteristic deflection on the existing pavement worked out by the HRS and for the designed traffic intensity in msa. The pavement thickness has to be obtained from Fig 5. The existing pavement thickness is to be deducted from the total pavement thickness derived and the balance provided as overlay interms of WBM after picking the B.

T surface. Widening the Road The design width of Road pavement for a traffic volume is equal to its capacity of the Road. This can be computed by projecting present volume at an appropriate growth rate. Further, traffic fluctuates more on urban roads than on rural roads. These factors coupled with other urban characteristics make it necessary to design the urban roads on the basis of peak hour traffic rather than average daily traffic as in the case of rural roads.

Para 6. The Level of Service depends on factors, such as speed and travel time, freedom to maneuver, traffic interruptions, comfort, convenience and safety. Six Levels of Service are recognized commonly designated from A to F. Para 5. At this level volume of traffic will be around 0. Para 8. Para 4. Type of carriageway PCUs per hour Total design service volumes for different categories of urban roads Arterial Sub-arterial Collector 1 2 lane one way 2 2 lane two way 3 3 lane one way 4 4 lane undivided two way 5 4 lane divided two way - 6 6 lane undivided two way - 7 6 lane divided two way - 8 8 lane divided two way -- - Note: 1.

Arterial Road: Road with no frontage access, no standing vehicles, very little cross traffic 2. Sub Arterial Road: Roads with frontage access but no standing vehicles and high capacity intersections 3. Audit Approaches: A few cases of audit approaches on pavement design is given below. According to clause 4. But the following are frequently noticed. But pavement thickness designed adopting CBR value 2. Here filling of river sand is not required. Pavement thickness has to be redesigned on the basis of CBR value of subgrade formed with carted earth but this was not often done involving extra pavement thickness.

This led to extra pavement thickness vide pavement design catalogue of IRC The entire sub grade was removed to a depth of mm, and replaced with river sand and the pavement was designed with CBR value of 7 for the sub grade. It was also seen that the berms and embankment were formed with earth having a CBR value 14 or 15 with lesser cost.

According to clause 5. But design life of 15 years is adopted for many cases. This resulted in extra cost. Verify whether latest traffic census was adopted for computation of design traffic in msa and correct CBR value is adopted for computation of pavement thickness.

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Cases are noticed on extra pavement thickness due to erroneous computation of design traffic. This resulted in providing excess overlay by way of excess thickness ranging from 10 mm to 23 mm. This excess provision of DBM resulted in an extra expenditure of 0. While designing the estimates for widening and strengthening 12 radial roads leading to Madurai city, HRS adopted census instead of census in respect of nine roads. As per census there was marked decrease in respect of five roads due to formation of ring roads in , change in flow of traffic to another road, upgraded as NH from The decrease in traffic required less overlay thickness as per specifications.

The adoption of census resulted in provision of 15 to mm of BM and DBM excess over requirement as per specifications, resulting in extra expenditure of Rs. Cases where strengthening the existing road sanctioned and Benkelman Bean Deflection Test was carried but and strengthening work not carried.

In the meantime special repair work either on flood restoration work or under other scheme carried out and strengthened the pavement. This involved extra cost on the work to the extent of addition to the pavement structure. Cases of designing existing the road for strengthening adopting IRC was noticed even without considering the existing pavement thickness of various layer.

Though the result of Benkelman Bean Deflection Technique Test result was not available, atleast the existing pavement had to be taken. If not done, the extra pavement thickness has to be worked out and commented. Failure to adopt IRC SP resulted in unnecessary extra pavement thickness involving extra cost. Pavement thickness has to be designed based on CBR value and traffic intensity for new road or widening. The pavement thickness has to be modified at intervals say 1 km based on the CBR value vide clause 3.

But uniform pavement thickness was adopted involving extra cost on extra thickness on various layers of pavement. In case of strengthening the existing pavements uniform pavement thickness adopted irrespective of modifying the pavement thickness on the basis of the result. The above case led for extra pavement thickness involving extra cost. This resulted in Paved shoulder, cycle tract were constructed adopting same pavement thickness of the main carriageway instead of standard specification prescribed by Government of India in letter dated Cases of not considering 25 mm SDBC towards total pavement thickness.

As 25 mm BC is enough for improving the quality as per MORTH guidelines since the roads needed only a thin surface treatment for improving the quality. The provision of additional 15 mm thick resulted in on extra expenditure of Rs 6. In case where strengthening and widening was carried out simultaneously, the bituminous binder and wearing course designed for widening portion is adopted for the strengthening portion of the existing carriageway, instead of designing the existing carriageway separately adopting IRC involving unwanted provision of overlay, extra overlay thickness.

The capacity of the road that could cater the traffic for the designed life is indicated in the above table for single intermediate, double lane etc. But cases where widening was carried out viz. This unnecessary widening resulted in extra cost. In respect of two roads the design service volume expected at the end of design life computed on the basis of census was PCU and PCU respectively at the end of design life. The intermediate layer was sufficient to cater the expected volume 5.

But the roads were upgraded as double lane and widened to 7 m width involving excess width of 1. This lead to an avoidable extra expenditure of Rs 1. Maintenance operation is classified into 3 groups -Routine Maintenance i. The periodicity of the renewal indicated therein should only be taken as general guidelines for the purpose of budgeting and determining the extent of renewal programme.

How can I get a copy of a DMRB/MCHW document?

It does not indicate the expected life. Normally 20 mm thick premix carpet, mix seal or SDBC may also be provided depending on traffic intensity. BC shall be laid only where the existing surface has BC as wearing course shall be adopted. Audit Approach: It was noticed that for periodical renewal 40 mm thick BC was provided instead of 25 mm thick.

This involved extra pavement thickness. The barrier type of kerbs with a height of mm should be buried to a depth of mm below the top level of pavement of the road and the mountable type of kerbs with a height of mm should be buried to a depth of mm. Audit Approach: To see whether the prescribed size of kerb was used or higher size adopted resulting in extra cost due to adoption of higher size.

The bridges shall be classified as minor bridge and major bridge. Minor bridge — Bridge having a total length upto 60 metres. Clause The bridges are designed and constructed adopting the following IRC specifications. Component of Bridge The component of the bridge is broadly grouped into i Foundation ii Substructure iii Superstructure The foundation are different type viz.

The substructure is the portion of the bridge structure such as pier and abutments above the foundation unit and supporting the superstructure. It shall also include returns and wing walls but exclude bearings. Superstructure is the portion of bridge structure above the substructure level viz.

Definition Clearance: Is the shortest distance between the boundaries at a specified position of a bridge. Free Board for highlevel bridge shall in no case be less than mm Linear Water way: is the width of waterway between the extreme edge of water surface at the highest flood level measured at right angles to the abutment faces.

Effective Linear Water way: is the total width of the waterway of the bridge at HFL minus the effective width of obstruction. Afflux: The rise in flood level of the river immediately on the upsteam of the bridge as a result of obstruction to the natural flow caused by the construction of bridge and its approaches.

Scour Depth: In natural stream, the scouring action of the current is not uniform all along the bed width particularly at the bends and also round obstructions to the flow eg. The piers of bridges there is deeper scour than normal. The assessment of the scour depth is relevant for the design of bridge foundations and protective works.

Whenever possible such assessment should be based on data made available from actual sounding taken at the proposed bridge site or in its vicinity. Such soundings are being taken during immediately after a flood before the scour holes have had time to silt up appreciably. Necessary allowance shall be made in the observed scour depth for increased depth for various reasons. Vertical clearance: Adequate vertical clearance shall be provided in case of all high level bridges which is usually the height from the designed HFL with afflux to the lowest point of the bridge superstructure.

Such clearance shall be allowed as follows. Discharge in cu. In case of slab bridges the difference between deck level and affluxed HFL shall not be less than 1. Determination of design discharge clause of IRC 5 The length of the bridge required to be constructed is primarily based on design discharge. If the data is not available it will be determined by the following method. Wherever possible more than one method shall be adopted, results compared and the maximum discharge fixed by judgement by the engineer responsible for the design.

Wherever footpaths are provided the width shall not be less than 1. The width of the median in the bridge portion shall be kept same as that in the approaches. Overall width of CD works Clause 7. As per current practice culverts are designated as 2,3,4,5 and 6 m slabs culvert or mm single to 6 rows pipe culvert etc. An efficient electric rail system connecting Takapuna and the current busway route to Wynyard and the CRL. My understanding is that going north i. Coming south i.


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I thought I saw a sign forbidding trucks to use the center lane 3rd when the bridge is in configuration. I appreciate a truck breaking down in that lane precludes any attempts to remove it until the barrier is moved. There are no restrictions on trucks on the harbour bridge, the clip ons were strengthened in A good idea but even now, unless there has been a crash, even at peak, the bridge flows pretty well. There almost is southbound. Buses use the left lane southbound, with a bus lane at either end. Fewer cars want to be in that lane.

Northbound is not so good as there are no bus lanes northbound. I suspect this was to allow people to get to work on time, but less important they get home on time.


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  6. Similarly Onewa Rd had a city-bound bus lane for years, but the return journey could easily take twice as long…. And the rest.

    Roads & bridges

    The homeward bound bus lane on Onewa Rd had only just gone in. The biggest bottleneck for buses around the bridge at the moment is northbound Fanshawe St onramp to Curran St Onramp. The almost-never-needed southbound Bus lane on the other side of the motorway must be the stupidest thing ever. I wish. Would both spans be two-way or would one be for north and the other for south? If the latter, there would likely be about years of capacity on each. And you do run into the problem of capacity of the motorways which would lead to huge back-ups.

    But putting the new bridge approaches roughly where the current ones are now would have the same effect. The perception would be that the new bridge was a couple billion dollars to make things worse and it would be true. I agree that the current bridge should be maximised for transit. The fifth lane at the peaks would allow one to be dedicated PT and still four available for cars. It would be worth a try. This is a road bridge, and should remain so.

    Transit use, and therefore its relief to traffic demand, will be optimised by making the next route a dedicated Rapid Transit one. Rail tunnels. Much cheaper to build too. The busway performs about as well as the southern line for patronage, and about the same on speed. As you point out, Onewa is the southbound bottleneck and the whole CBD is the northbound bottleneck. Excellent graphs. The last one shows the available useful capacity between the morning and evening peaks. As demand grows from around vph to vph in those hours we will see why more capacity will be needed or why the existing capacity will need to be reallocated either through occupancy restrictions or pricing.

    And if we build rail to the shore then probably delays it even further if not all together. The costs of any additional crossing are huge and can be delayed by finessing the buses so much more. However it is clear that the missing trick across the harbour after the Active modes which are about to be added is a dedicated Transit route not additional traffic lanes which just cause huge additional costs and burdens on the road networks and land use on either side.

    And a pair of rail tunnels will provide a service so direct and fast between key city and Shore points as to be irrestable for thousands, keeping the bridge at an optimal utility indefinitely. Plus, half way between the end of the green line and the edge of the graph, we will see the effect of the Waterview connection to the second harbour road crossing that we already have. Would be interesting to know how much traffic this would remove from bridge. Tram network could then be progressively expanded up the northern busway. I guess I am thinking that it would be a lot cheaper than building a tunnel.

    What is the difference between a tram and a light rail? My understanding was that it just depends on the frequency of stops. They tend to be slow, fairly low capacity and unreliable. Light rail tends to be much longer vehicles roughly train sized that run either entirely off street, or if they are on street they have dedicated separate running way, priority or grade separation at intersections, etc. I was wondering about the capacity of the northern busway. You mention buses southbound during peak hour.