diff --git a/include/sta/TimingArc.hh b/include/sta/TimingArc.hh
index 00cea66b..0deb1d4a 100644
--- a/include/sta/TimingArc.hh
+++ b/include/sta/TimingArc.hh
@@ -258,6 +258,8 @@ public:
   TimingArc *cornerArc(int ap_index);
   void setCornerArc(TimingArc *corner_arc,
 		    int ap_index);
+  float driveResistance() const;
+  float intrinsicDelay() const;
 
   static bool equiv(const TimingArc *arc1,
 		    const TimingArc *arc2);
diff --git a/liberty/Liberty.cc b/liberty/Liberty.cc
index 4b0f8d16..91754417 100644
--- a/liberty/Liberty.cc
+++ b/liberty/Liberty.cc
@@ -2011,11 +2011,10 @@ LibertyPort::driveResistance(const RiseFall *rf,
 	TimingArc *arc = arc_iter.next();
 	if (rf == nullptr
 	    || arc->toTrans()->asRiseFall() == rf) {
-	  GateTimingModel *model = dynamic_cast<GateTimingModel*>(arc->model());
-	  if (model) {
-	    float drive = model->driveResistance(liberty_cell_, nullptr);
-	    if (min_max->compare(drive, max_drive))
-	      max_drive = drive;
+          float drive = arc->driveResistance();
+          if (drive > 0.0) {
+            if (min_max->compare(drive, max_drive))
+              max_drive = drive;
 	    found_drive = true;
 	  }
 	}
@@ -2049,18 +2048,13 @@ LibertyPort::intrinsicDelay(const RiseFall *rf,
 	TimingArc *arc = arc_iter.next();
 	if (rf == nullptr
 	    || arc->toTrans()->asRiseFall() == rf) {
-	  GateTimingModel *model = dynamic_cast<GateTimingModel*>(arc->model());
-	  if (model) {
-	    ArcDelay arc_delay;
-	    Slew slew;
-	    model->gateDelay(liberty_cell_, nullptr, 0.0, 0.0, 0.0, false,
-			     arc_delay, slew);
-	    float delay = delayAsFloat(arc_delay);
+          float delay = arc->intrinsicDelay();
+          if (delay > 0.0) {
 	    if (min_max->compare(delay, max_delay))
 	      max_delay = delay;
 	    found_delay = true;
 	  }
-	}
+        }
       }
     }
   }
diff --git a/liberty/TimingArc.cc b/liberty/TimingArc.cc
index 55a3d4f9..92d6396d 100644
--- a/liberty/TimingArc.cc
+++ b/liberty/TimingArc.cc
@@ -134,6 +134,34 @@ TimingArcAttrs::setOcvArcDepth(float depth)
   ocv_arc_depth_ = depth;
 }
 
+float
+TimingArc::driveResistance() const
+{
+  GateTimingModel *model = dynamic_cast<GateTimingModel*>(model_);
+  if (model) {
+    LibertyCell *cell = set_->libertyCell();
+    return model->driveResistance(cell, nullptr);
+  }
+  else
+    return 0.0;
+}
+
+float
+TimingArc::intrinsicDelay() const
+{
+  GateTimingModel *model = dynamic_cast<GateTimingModel*>(model_);
+  if (model) {
+    LibertyCell *cell = set_->libertyCell();
+    ArcDelay arc_delay;
+    Slew slew;
+    model->gateDelay(cell, nullptr, 0.0, 0.0, 0.0, false,
+                     arc_delay, slew);
+    return arc_delay;
+  }
+  else
+    return 0.0;
+}
+
 ////////////////////////////////////////////////////////////////
 
 TimingArcSet *TimingArcSet::wire_timing_arc_set_ = nullptr;